In order to implement the Plan of Food Contamination Monitoring and ensure the accuracy and reliability of monitored data, we carried out a program of quality control for determination of lead, arsenic, cadmium and mercury in ten labs of 10 provinces in 2000 and 2001. The results indicated that the contents of arsenic and cadmium in one of the 10 labs were out of 3 standard deviations. There was also a great systematic errors in the determination of lead as the contents of lead in 7 of 10 labs were higher than the standard value. There was also a great variation in the determination of lead in 2000. The quality of analysis improved after recognition of the causes in 2001. There after, the results of determination of lead in 6 of 10 labs were in the standard range while all the determination were within the 3 standard deviation.