1. A bad pixel correction method for an image, comprising: determining whether each of pixels of a predetermined block in the image is a bad pixel sequentially; when a current pixel of the block is determined to be bad and a temperature value is higher than a threshold, re-determining that at least one previously determined pixel in the predetermined block to be bad, wherein the previously determined pixel is adjacent to the current pixel; and correcting the current pixel and the previously determined pixel; wherein the step of determining whether each of the pixels of the predetermined block comprises: generating a horizontal luminance difference, a vertical luminance difference, a main diagonal luminance difference and an opposite diagonal luminance difference according to a luminance value of the current pixel and luminance values of pixels around the current pixel in the predetermined block; generating a minimum luminance difference according to the horizontal luminance difference, the vertical luminance difference, the main diagonal luminance difference and the opposite diagonal luminance difference; generating a first compensation luminance value and a second compensation luminance value according to the minimum luminance difference, the horizontal luminance difference, the vertical luminance difference, the main diagonal luminance difference and the opposite diagonal luminance difference; and determining whether the current pixel is a bad pixel according to the minimum luminance difference and a predetermined luminance difference; wherein the correcting step comprises: determining a compensation luminance value of the current pixel according to the first compensation luminance value, the second compensation luminance value or according to the first compensation luminance value, the second compensation luminance value and the luminance value of the current pixel; and determining a compensation luminance value of the at least one previously determined pixel in the block; wherein the step of determining whether each of the pixels of the predetermined block further comprises: amplifying the minimum luminance difference by one, two, three and four; and comparing the minimum luminance difference, two times the minimum luminance difference, three times the minimum luminance difference and four times the minimum luminance difference with the predetermined luminance difference, respectively, wherein the step of determining whether the current pixel is a bad pixel according to the minimum luminance difference and the predetermined luminance difference comprises: determining that the current pixel is a bad pixel, if the minimum luminance difference is larger than the predetermined luminance difference and the luminance value of the current pixel is larger than a one-second summation of the first compensation luminance value and the second compensation luminance value; determining that the current pixel is a bad pixel, if two times the minimum luminance difference is larger than the predetermined luminance difference and the luminance value of the current pixel is larger than a one-third summation of the first compensation luminance value, the second compensation luminance value and the luminance value of the current pixel; determining that the current pixel is a bad pixel, if three times the minimum luminance difference is larger than the predetermined luminance difference and the luminance value of the current pixel is larger than a one-fourth summation of the first compensation luminance value, the second compensation luminance value and a double luminance value of the current pixel; determining that the current pixel is a bad pixel, if four times the minimum luminance difference is larger than the predetermined luminance difference and the luminance value of the current pixel is larger than a one-fifth summation of the first compensation luminance value, the second compensation luminance value and a triple luminance value of the current pixel; and determining that the current pixel is not a bad pixel, else.