The Anhui Experiment of Yangtze Project，conducted in October 2015, is a large active source experiment using air-gun sources. It is the first 3 dimensional seismic survey with active sources in the Yangtze River，with exciting air guns in 20 fixed spots as the seismic source,109 permanent stations and a network formed by 11 portable survey line as the observation system. Using the data from permanent stations，we studied the seismic signals generated by air guns in the Yangtze River. The results show that the air gun signals are clearly seen in permanent stations' records，to a maximum distance of 300km. Further analysis on absolute amplitude of air gun signals shows that (1)the strength of air gun signals has scale of about 10nm at 50km away from the source，and it reduces significantly to less than 1nm at 200km; (2)an azimuthal anisotropy is observed in spatial distribution of air gun signals' strength，which may be related to the geometry of Yangtze River; (3)a low ambient noise level is essential for retrieving weak air gun signals from the records，and high quality of permanent stations network run by Chinese Earthquake Administration offers a great opportunity to retrieving air-gun signals with amplitude as small as nanometers.