Binchuan Transmitting Seismic Station usesa large-volume air gun array as seismic source，which can continuously activate highly repeatable signal. We analyzed the seismic data collected in 2013 and did observations on the subsurface structure. Due to the influence on the waveform of the source and far-field air-gun signals by the water level change of the reservoir，the characteristics of source signals from an air-gun array in a reservoir and proper data processing flow were studied for the need of differentiating the structure variation and source variation. The results show that: (1)When the reservoir water level variation is large，the cross-correlation coefficient between the seismic waveforms recorded in the same station is too low. Under this condition，we can't do direct stacking to the data，but should do source cluster analysis first. The result of the analysis is governed by the amount of water level change. (2)In order to eliminate the influence of water level change，we conducted a deconvolution process. When the epicentral distance is less than 10km，stack method for multi-shot air-gun data is used to activate in different water levels. Deconvolutionhas a better result than direct stacking. (3)By cross-correlation and SNR analysis，we found that 4 stations have waveform variations which may be caused by subsurface structure variations.