Objective To investigate the effect of different doses of ketamine pretreatment on propofol‑induced involuntary body movements in children and to find the best dose. Methods Using random number table method, 150 pediatric patients undergoing elective surgery under general anesthesia (86 males and 64 females, aged 3‒12 years, American Society of Anesthesiologists (ASA) physical status Ⅰ or Ⅱ) were divided into propofol group (group P), ketamine 0.5, 0.6, 0.7, 0.8 mg/kg group (groups K1, K2, K3 and K4), with 30 cases in each group. Patients in group P were intravenously administered with 3 mg/kg propofol; patients in groups K1, K2, K3 and K4 were injected with corresponding doses of ketamine 2 min before propofol, followed by the same amount of propofol administration. The general data, operation time, anesthesia time, heart rate (HR), respiratory, mean arterial pressure (MAP) and pulse oxygen saturation (SpO2) at induction (T0), intubation (T1), and operation initiation (T2), as well as incidence of body movements, extubation time, adverse reactions during anesthesia recovery, Ricker Sedation Agitation Scale (SAS) and Ramsay score were compared among the groups. Results There were no significant differences in general data, operation time, anesthesia time, HR, MAP, SpO2, SAS and Ramsay score at different time points among the 5 groups (P>0.05). The incidence of body movements in groups K2, K3 and K4 was significantly lower than that in group P (P<0.05), and that in groups K3 and K4 was lower than that in group K1 (P<0.05). However, the extubation time in group K3 and group K4 was significantly longer than that in group P (P<0.05), as well as that in group K1(P<0.05）, and that in group K4 was significantly longer than that in group K2 (P<0.05）. There was no significant difference in the incidence of adverse reactions in each group during anesthesia recovery (P>0.05). Conclusions Small dose of ketamine can safely and effectively reduce the incidence of involuntary body movements induced by propofol in children and 0.6 mg/kg is the best dose.