Abstract: The methods were developed to determine the residues of chlorothalonil and thiram in mushroom,their dissipation rates and final residues were also studied.Chlorothalonil was determined by GC with ECD-detector,and thiram was determined by HPLC with UV-detector.The average recoveries and coefficient variation of the methods were 90.19%~99.11% and0.9%~3.2% for chlorothalonil,and 73.94%~86.47% and 2.6%~15.8% for thiram,respectively.The limit of detection for chlorothalonil and thiram were 1×10-12 g and 6×10-9 g,and the limit of quantification were(0.01 mg/kg) and 0.3 mg/kg,respectively.The results showed that the half-lives of chlorothalonil and thiram in mushroom were 2.5 days and 4.2 hours,respectively,at double of the recommended dosage.The study revealed that the residues of chlorothalonil in mushroom were above the MRL in China (1 mg/kg) after 5 days at the recommended dosages(1 800 g/hm2) and double of that, however,the residues of thiramin mushroom were below the MRL(3 mg/kg) after 2 days.The results indicated that chlorothalonil is unsuitable for mushroom in a greenhouse,but thiram is permitted to applicate on mushroom.