The influence of signal-to-noise ratio (SNR) of spatial low-coherence interference on demodulated interference order jump and absolute phase, combining with monochromatic frequency absolute phase demodulation algorithm，is simulated and analyzed. The simulation result shows that it can avoid interference order jump when SNR exceeds 18 dB. In this case, standard deviation of demodulated absolute phase decreases linearly with the increase of SNR, and the value of standard deviation with SNR of 25 dB drops to 0.023 rad. The experiment about the influence of SNR on pressure demodulation is investigated through changing optical source intensity, and the experiment result is consisted with the simulation analysis. Pressure demodulation experiment shows that demodulation error decreases with the increase of SNR. Pressure demodulation error is 0.044 kPa when SNR reaches up to 24.79 dB, reduced 2.84 times compared to that with SNR of 18.10 dB. Experiment results indicate that when the pressure is in the range from 5 to 150 kPa, only the value of SNR is greater than 22 dB, and the demodulation accuracy can meet 0.05% F.S.，where F.S. is full scale.