To study the activity of fish in a coastal area of the Yellow Sea, the first acoustic survey of fishery resources was carried out from November 22 to December 5, 2015 using the self-developed research-type fish finder, to obtain the fish activities data. First of all, four sets of fish finder instrument were put at four fixed points of the investigated area to monitor the fish stocks entering the area, and the echo data of fish was collected and analyzed and dealt with using acoustic technology, thus to get the distribution of the fish target strength in the vertical direction, the target strength size distribution of fish, and the distribution of fish amount in different water layers and at different time, as well as the amount of fish resources. Results showed that fish in the investigated sea area were mainly distributed in the layer of 4~10 m, and with the gradually increasing of the water depth, the amount of fish became smaller. In the investigated sea area, the fish activity frequency showed an increasing trend from 9am to 1pm, and reached the peak between 1pm to 2pm which was about 0.38. The fish target strength of -49~-40 dB accounted for the highest proportion, and the strength higher than -40 dB was evenly distributed in the whole water layers, while that smaller than -40dB was mostly distributed in the shallow water layer of 4~10 m. Survey results showed that the acoustic technology could monitor fish activities, and the fish target strength distribution was relatively concentrated in the investigated sea area. In the depth direction, the fish was mainly concentrated in the upper layer. The activities of fish in different time periods changed along with the variation of temperature: when the temperature rose, the frequency of fish activity increased, otherwise the frequency of fish activity decreased, from which we can conclude that most of the fish species in the investigated area were warm water species.