Abstract: Double frequency method of conventional eddy current testing technology to inspect the austenitic stainless steel heat exchanger tube was introduced. It showed that the curve of phase against thickness decrease was greatly different from the stand curve in several kinds of literatures. The difference between the nature defect and artificial defect signals was compared, and the false defect signal excited by step-change of thickness in heat exchanger tube formed in manufacturing process was analyzed. Defect could be inspected by the assistant function(Altitude-Phase Warning). Through the analysis of the value of eddy current testing, it conclude that eddy current testing was in advantage of high speed, low prices, and being effect in inspecting the austenitic stainless steel heat exchanger tube.