High-purity Indium is one of the original materials of InSb. The type and content of the trace elements directly influence the performance of the detector. Therefore it is particularly important to establish the accurate and efficient quantified method. By strictly controlling the temperature to ensure the realization of the acid hydrolysis process, a standard addition method was used to establish a standard curve and test the sample. After comparing the response rates, the selected base sample for this test was In single standard solution with a concentration of 10 ppb, and the linear correlation coefficients of the standard curve were close to 0.999. Excluding the influence of liner differences, the test results of multiple batches were analyzed to verify their accuracy. At the same time, the internal standard method was used to verify the content of various impurity elements in the In10000 solution. The results show that the base sample has extremely low impurity content. The accuracy and repeatability of this testing method were verified multiple times by configuring a solution with known standard concentrations. The test results show that this testing method is accurate and effective, and can be applied to the impurity content testing of high-purity (greater than 6N) In.