Among all the measurement methods on activity of urease, indophenol blue colorimetric method, higher accuracy of the measurement results and better reproducibility, is the most widely used measurement method on activity of urease. However, this kind of method also owns some drawbacks, for examples, filtered fluid of cultivated soil is muddy and concentration of substrate has a great influence on the activity of urease. Based on the former measurement methods, four crucial parameters was taken to, such as method of filtration, time of cultivation, concentration of substrate and choice of buffer solution, the comparative tests in order to improve the accuracy of the measurement results of indophenol blue colorimetric method. The result of improved method is closer to the real activity of urease in soil with the conditions that choosing 5% concentration of substrate and pH10.0 borate buffer solution during the cultivation, extracting and filtrating with potassium chloride solution after 24-hours cultivation. The result of improved indophenol blue colorimetric method is 2.46 times better than the traditional method.