The ranging performance of radar is based on its performance of echo detection.Generally the echo signal of radar is too small to detect,in order to detect the small useful signal,it is a method to accumulate the echo wave within video-frequency or within mid-frequency.This paper analyzes the increased ratio of echo's SNR(signal-to-noise rate) and the according pulse accumulation method is designed and realized by digitalizing the echo and synchronously accumulating them in FPGA(field programmable gate array),which improves that the SNR of accumulation of ten time-cycles is ten times than that of no accumulation.Although the method of accumulation is used in the field of radar,it can be used in the other fields,such as,in the research on biological medicine electric measurement.