The large number of sampling point for Beidou B2 satellite navigation signal causes heavy calculation cost in acquisition, which will result in slow acquisition speed and difficult hardware implementation. A fast acquisition algorithm based on the modified averaging correlation method and the traditional parallel code phase acquisition method is proposed. The suggested algorithm reduces the sampling number from 11 428 to 2 048 by averaging sampling and during which the samples grouped together do not cross sign bit, therefore, the signal energy loss is avoided. Simulation experiment based on simulated signal source is conducted and peak-to-peak radio (PPR) is adopted for quantitative analysis of acquisition performance. Experimental result indicates that the acquisition accuracy of the proposed algorithm is almost the same with the traditional algorithm while it saves nearly half of the amount of calculation. Besides, the hardware implementation of 2 048 fast Fourier transform (FFT) is much easier than 11 428 FFT which is helpful for more realtime of software receiver.