Ｏｂｊｅｃｔｉｖｅ　To observe and compare the effects of different priming doses on the neuromuscular block effects of mivacurium．　Methods　A total of forty patients of ASA Ⅰor Ⅱ, who were scheduled for elective surgery under general anesthesia, were randomized into four groups(n=10): control group(group A), 20% 95% effective dose(ED95) of mivacurium as the priming dose group(group B), 30%ED95 of mivacurium as the priming dose group(group C), 40%ED95 of mivacurium as the priming dose group(group D). Following induction of anesthesia with sufentanil and propofol, group A received normal saline, group B received mivacurium 0.014 mg/kg as a priming dose, group C received mivacurium 0.021 mg/kg as a priming dose, group D received mivacurium 0.028 mg/kg as a priming dose. After a 2 min priming time, intubation doses of mivacurium were given(group A 0.210 mg/kg, group B 0.196 mg/kg, group C 0.189 mg/kg, group D 0.182 mg/kg). TOF-Watch acceleration monitoring instrument was used for muscle relaxation. The time of neuromuscular block onset，duration of peak effect, duration of blockade maintenance, duration of in vivo action and recovery index were recorded.　Results　Onset time in group B, C and D was similar(P>0.05), but was significantly shorter than that in group A[group A (183±48） s, group B(141±18) s, group C(132±30) s, group D(117±21) s](P<0.05). There was no significant difference in duration of peak effect，duration of blockade maintenance，duration of in vivo action and recovery index was observed among the four groups(P>0.05).　Conclusions　Priming with a 2 min priming interval significantly accelerated onset of mivacurium, and it did not affect the clinical duration and recovery profiles of mivacurium. However, there was no significant difference by increasing priming doses.