1. A fingerprint identification method, comprising: obtaining an object image by a fingerprint sensor, and storing a plurality of pixel data of the object image in a first color model format by a memory, wherein the pixel data comprise a plurality of first pixel values; converting the pixel data into a second color model format by a processor, and obtaining a plurality of second pixel values based on the converted pixel data and a first gain value by the processor; calculating a plurality of third pixel values based on the first pixel values and the second pixel values by the processor; calculating a first standard deviation based on the third pixel values by the processor; and determining whether the first standard deviation is greater than a first preset threshold value by the processor, if the first standard deviation is greater than the first preset threshold value, recognizing the object image as a fingerprint image of a true finger by the processor, wherein the step of calculating the third pixel values based on the first pixel values and the second pixel values comprises: subtracting the second pixel values from the first pixel values for obtaining the third pixel values by the processor.