In BeiDou satellite receiver, a fast BeiDou signal acquisition algorithm based on coherent down-sampling was proposed to solve the problem that the large amount of data to be processed by the Fourier transform affects the acquisition speed of satellite signals in the traditional parallel frequency acquisition algorithm. On the basis of FPGA+DSP (field-programmable gate arrays+digital signal processors), the coherent down-sampling module was added to the traditional parallel frequency acquisition algorithm, and after the carrier and pseudo random code were stripped, the sampling frequency was reduced to decrease the number of points to be processed in the Fourier transform, and then a three-dimensional search for the satellite signal was performed. Theoretical analysis shows that the algorithm can reduce the amount of calculation by more than 80%; the experiments on the actual BeiDou signal indicate that the average acquisition time of each star is 9.95 ms, and the memory resource consumption is reduced by 42% compared with the traditional parallel frequency acquisition algorithm. This algorithm can effectively improve the acquisition speed while saving resources, which can provide reference for further improving the acquistition performance of the software receiver.