The invention relates to a Beidou signal capturing method in a weak signal environment. The method comprises the following steps: S1, arranging a down-conversion unit and carrying out down conversion processing on a received intermediate-frequency sampling signal; S2, carrying out NH code stripping on the received signal respectively, carrying out transformation into a frequency domain signal, carrying out multiplying with a multiplexing sum of a local code frequency domain value and then carrying out inverse transformation into a time domain; S3, carrying out conjugate multiplication on a coherent accumulation value at current time and a coherent accumulation value at previous time and carrying out summation; and S4, carrying out taylor series expansion on an amplitude difference value of two-side spectral lines of the peak value of the coherent integration result, deriving a quasi-linear relation of a frequency value and the amplitude difference value, and solving a frequency estimation value by using the linear relation. According to the invention, correlation calculation can be carried out on coherent values corresponding all code phases by one time; the signal to noise ratio is improved and the detection efficiency is improved; and the squaring loss of the non-coherent integration can be reduced. A problem of bit flipping caused by navigation data modulation can be solved, thereby improving the detection probability; the code phase and carrier wave frequency-offset estimation precision is enhanced; and the calculating speed and the calculating precision are guaranteed and the good stability and practicability are realized.