Ten dogs weighed 8.5～16.4kg were selected to determine the safe dose of methyl tert butyle ether (MTBE) for dissolving gallstones in vivo and its toxic and side effects. A couple of human gallstones type Ⅰ and type Ⅳ were put into each dog's gallbladder connecting outside with a silicon gel tube from which MTBE was administered at intervals with random doses. The vital signs were observed during the course of operations. Moreover liver and renal functions were tested before and after operations. Results: ①All gallstones type Ⅰ and Ⅳ in animal models were dissolved quickly, however, MTBE showed somewhat toxicity in inhibiting CNS, so that the dose of MTBE should be controlled precisely. ②No abnormal change of liver and renal functions of dogs were found before and after operations. ③Choloecyst pathological sections of gallbladder suggested that no evident of damage and inflammation of gallbladder was of found. Hemopexis with reversible histological change was observed in hepatic sinusoid and centeral vein short time after administation of MTBE.