We used the data of Xinjiang Digital Seismic Network and PSD(power spectral density)method to do the noise level assessment for six stations. We calculated the median of the power spectral density to evaluate the noise level of different stations. After the comparison of the power spectral density of different stations and the air-gun signal recognition，we found that noise level of the stations with recognizable air-gun source signals is lower than that of the stations without recognizable signals. The largest difference of the power spectral density is 40dB，and the smallest one is 15dB. Finally，we found that the failure to recognize the signal of air-gun source at some stations is due to the noise level.