Dredging and reclaiming on coast, harbor construction etc. of when construct, the interest about efficiency and accuracy of sounding by measurement condition very rise. However, there are only a few studies on the accuracy improvement concerning water depth sounding condition. In this study, among the precision decline main causes of sounding, 1 suggested the characteristics of sounding data acquired by echo sounder with increasing of turbidity and the critical turbidity range under a given transducer frequency. For this, I acquired sounding data by inputting turbidity inducer artificially in artificial water tank. And then achieved regression analysis. Conclusion are as following Sounding Capabilities can be divided into three ranges according to the turbidity . normal range, critical range and the range where data can not be obtained by an echo sounder. When the turbidity exceeds $217~259$ NTU which was considered as critical range, depth sounding was impossible.