Based on the comprehensive standard deviation formula measuring the accuracy of flow, the safety and accuracy of the eror index val-ues have been improved with a confidence level 85% and comprehensive calculation.Also, the two practical solutions measuring type Ⅲ erorus-ing mono-static calculation method and comprehensive calculation method were given based on the analysis of the experiment data of 296 typelerrors at the 1l5 stations, which has effctively controlled the eror of flow and improved the accuracy of flow.And the comprehensive calculationmethod is better than the mono-static calculation method. The conclusion of the research has largely improved the related provisions of riverflowmeasurement specification and also provided important bases for the modification.