This study was performed to investigate the effect of co-existence of BPMC, carbaryl and chlorothalonil on the short-term bioconcentration factor in Carassius auratus(goldfish). The fishes were exposed to the combined treatment of BPMC, carbaryl and chlorothalonil (0.05 ppm+0.05 ppm+0.005 ppm, 0.05 ppm+0.05 ppm+0.010 ppm, 0.05 ppm+0.10 ppm+0.005 ppm, 0.10 ppm+0.05 ppm+0.005 ppm, 0.10 ppm+0.10 ppm+0.005 ppm) for 3 and 5 days, respectively. BPMC, carbaryl and chlorothalonil in fish and in test water were extracted with n-hexane and acetonitrile. GC-ECD was used to detect and quantitate BPMC, carbaryl and chlorothalonil. 3-day and 5-day bioconcentration factors(BCF$_3$ and BCF$_5$) of each pesticide were calculated from the quantitation results. The depuration rate of each pesticide-from the whole body of fish was determined over the 72-h period after combined treatment.The results were as follows: BCF$_3$ values of BPMC were 4.163, 4.011, 4.122, 4.750 and 4.842 when the concentration of BPMC+ carbaryl+chlorothalonil in combined treatment were 0.05 ppm+0.05 ppm+0.005 ppm, 0.05 ppm+0.05 ppm+0.010 ppm, 0.05 ppm+0.10 ppm+0.005 ppm, 0.10 ppm+0.05 ppm+0.005 ppm and 0.10 ppm+ 0.10 ppm+0.005 ppm. BCF$_5$ values of BPMC were 3.465, 3.270, 3.472, 3.162, 4.227 and 4.157, respectively, under the above conditions. While BCF$_3$ values of carbaryl were 4.583, 4.642, 4.571, 3. 637 and 3.529, respectively, and BCF$_5$ values of carbaryl were 3.932, 3.797, 3.843, 4.293 and 4.132, respectively, under the conditions. While BCF$_3$ values of chlorothalonil were 2.024, 3.532, 2.213, 2.157 and 2.271, respectively, and BCF$_5$ of chlorothalonil were 6.712, 7.013, 6.457, 6.694 and 6.597, respectively, under the conditions. Depuration rate constants of BPMC were 0.019, 0.018, 0.020, 0.022 and 0.021 when the concentration of BPMC+carbaryl+chlorothalonil in combined treatment were the same as above. And depuration rate constants of carbaryl were 0.030, 0.029, 0.030, 0.029 and 0.031, respectively, under the same condition of pesticide mixtures. While depuration rate constants of chlorothalonil were 0.004, 0.004, 0.003, 0.004 and 0.003, respectively, under the same condition. It was observed that no significant differences of BCFs and concentrations of the compounds in fish extracts, test water between combined treatment and single treatment. It was considered that no appreciable interaction at experimental concentrations was due to low concentrations, near environmental level, 0.005-0.1 ppm. Coexistence of BPMC, carbaryl and chlorothalonil had no effect on depuration rate of each pesticide and depuration rate of chlorothalonil was investigated 1/8 and 1/6 slower than those of carbaryl and BPMC in combined treatment. It is similar result in comparison with single treatment. Therefore, it is considered that the persistence of chlorothalonil in fish body would be higher than those of carbaryl and BPMC.