With the globalization of BeiDou satellite navigation system, BeiDou receivers based on software defined radio (SDR) are used more and more popular in BeiDou navigation and positioning. However, in the high precision measurement applications, such as real time kinematic (RTK) application, the baseband sampling ADC in BeiDou receivers suffers the influence of sampling clock jitter, which is added with the inherent quantization noise and thermal noise, and generates neglectable influence on the ranging error. In this paper, the BeiDou published global signals B1I, B1C, B2I, B2a and B3I are analyzed firstly. Secondly, the math models of the sampling noises including the clock jitter, quantization noise and thermal noise in ADC sampling are described in detail. Thirdly, the synthesized SNR formula is proposed, and the general expression of the ranging error is derived from the carriertonoise ratio (C/N0). An engineering quantitative analysis method for selecting different parameters under high accuracy requirement is given. Furthermore, aiming at the influence of different parameters on the BeiDou signal ranging error, simulation analysis was performed. Simulation results show that under the goal of ranging error of 0.6cm, it is required that the sampling clock jitter should not exceed 45 ps, the central frequency of the receiver should not be larger than 80 MHz, the bandwidth should not be less than 25 MHz, the quantization bit length should not be less than 7 bits, and the C/N0 should not be less than 30 dB. Finally, the test experiment on the BeiDou signal B2I was conducted. Under the conditions of the sampling clock jitter of 35 ps, the receiver central frequency of 61.38 MHz, the bandwidth of 32 MHz, the quantization bit length of 12 bits, and the C/N0 of 67 dB, the solved ranging error is 0.41 cm, which verifies the effectiveness of the proposed method.