In this paper,the stability and accuracy of determination method for dichlorvos,phorate,dimethoate,methyl-parathion,malathion,chlorpyrifos and parathion in groundwater were verified by a balanced uniform-level experiment involving five concentration levels and seven laboratories collaboration.Seven organophosphorus pesticides were extracted from groundwater with dichloromethane solution containing about 5% acetone,and the quantitative analysis of organophosphorus pesticides was carried out by gas chromatography with flame photometric detector.The whole analysis processes in every research laboratory and every sample level gave three results for statistics.The presence of individual laboratories or values that appeared to be inconsistent with all other laboratories or values may change the estimates,therefore,decisions have to be made with respect to these values.The balanced uniform-level experiment can provide a deterministic way to prove the accuracies（trueness and precision） of determination method and result by Cochran-test and Grubbs-test methods.The scrutiny of statistical results of seven organophosphorus pesticides in groundwater for consistency and outliers showed that the determination method was stable within a level range of 20-2 000 ng/L after eliminating the outlier data.The average recoveries of determination method for these organophosphorus in different levels were in the range of 91.1%-109% with relative standard deviations of 2.2%-12.6%.The surrogate recoveries for triphenyl phosphate during the analysis process were 77.8%-119%.The detection method is accurate and reliable.