Abstract: In order to give the scope of error and enhance the reliability of test data, it is necessary to the uncertainty for coefficient of variation of drippers discharge. The comparison analysis for coefficient of variation of drippers discharge uncertainty evaluation method is supported by test data, so the effect and adaptability of two A—type uncertainty evaluation methods which based on series of test data were discussed. The conclusion was that the proportion of A—type standard uncertainty was more than B—type standard uncertainty which doesn’t based on series of test data among the compound standard uncertainty, and the expanded uncertainty of maximum entropy was higher 4% than normal method in 95% probability for A—type evaluation, and the density distributing function of maximum entropy method matched the test data preferably, and also eccentricity coefficient of maximum entropy method was adaptability, but the quantity of test date of maximum entropy method was over 1 times than normal method. The maximum entropy method, which can improve the accurate of uncertainty evaluation.