1. A method for analyzing ultrasound echo signals based on statistics of scatterer distributions, comprising steps of: obtaining an ultrasound image data, wherein the ultrasound image data has a plurality of ultrasound echo signals, each having a signal image value; choosing a first ultrasound echo signal as a center, calculating the signal image values of all ultrasound echo signals within a window block in the ultrasound image data, to obtain a first ultrasound scatterer value; choosing a second ultrasound echo signal as a center, calculating the signal image values of all ultrasound echo signals within the window block in the ultrasound image data, to obtain a second ultrasound scatterer value, wherein the second ultrasound echo signal is separated from the first ultrasound echo signal at least one point distance; at intervals of the point distance, repeatedly calculating the signal image values of all ultrasound echo signals within the window block with the respective ultrasound echo signals as centers, to obtain a plurality of ultrasound scatterer values, until the first ultrasound scatterer value to an n-th ultrasound scatterer value being obtained, wherein the ultrasound scatterer values are a measure of dispersion (MD) of the signal image values, a measure of location (ML) of the signal image values, or any combination thereof; and outputting an ultrasound scatterer mode image with the first ultrasound scatterer value of the first ultrasound echo signal to the n-th ultrasound scatterer value of the n-th ultrasound echo signal by utilizing color scale, wherein the ultrasound scatterer values are obtained by one of the following approaches: (a) dividing a first MD of the signal image values by a second MD of the signal image values, raising to a power constant, and multiplying by a weighting constant, (b) dividing a difference value between a first ML and a second ML of the signal image values by the MD of the signal image values, raising to a power constant, and multiplying by a weighting constant, and (c) dividing the MD of the signal image values by the ML of the signal image values, raising to a power constant, and multiplying by a weighting constant.