OBJECTIVE To study the muscular relaxat effect of cisatracurium in infants and young children with different dose under intravenous inhalational anesthesia, in order to discuss the reasonable using dosage. METHODS 168 cases of infants and young children were research object which was carried out surgery under Intravenous inhalational anesthesia in our hospital during 2015.10～2016.11. 168 cases of infants and young children were divided into group A(3～6 months)and group B(7～36 months) by age-group. Group A and group B was divided into two subgroups by loading doses of cisatracurium (2ED95 0.10mg/kg, 3ED95 0.15mg/kg). All four groups: group A0.10, group A0.15, group B0.10 and group B0.15, 25 cases per group. The muscular relaxat effect index (onset time, clinical action time, RI, Th time and TOF recovery time) and untoward effect was observed. RESULTS The onset time of group A was significantly shorter than group B(P<0.05) and the onset time of high loading doses group (0.15mg/kg) was significantly shorter than low loading doses group (0.10mg/kg) (P<0.05). The difference of clinical action time, recovery time and untoward effect had no statistical significance between four groups(P>0.05). CONCLUSION The age of infants and young children and loading doses of cisatracurium was the key factor of influencing muscular relaxat effect.