Abstract: Recombinant humanized anti-ricin monoclonal antibody (MIL50) is a recombinant humanized monoclonal antibody targeting ricin. In this study, an ELISA method was used to establish a method for the determination of MIL50 in macaque serum, and a cross design method was used. Twelve rhesus monkeys were intravenously injected 1 mg·kg^-1 test preparation (MIL50 freeze-died powder injection) and reference preparation (MIL50 liquid preparation) to determine the plasma concentration of MIL50 at different time points, and the pharmacokinetic parameters were analyzed to compare the pharmacokinetic characteristics of MIL50 liquid preparation and freeze-died powder injection in rhesus monkeys. Animal welfare and experimental procedures follow the regulations of the Animal Ethics Committee of the Chinese Academy of Medical Sciences and Use of Laboratory Animals and the regulations derived by the Animal Care and Welfare Committee of the Institute of Radiation Medicine, Academy of Military Medical Sciences (IACUC-DWZX-2020-503). The results showed that there was no significant difference between C_max and AUC_0-5d in the two groups. The liquid preparation was the reference preparation, with C_max ratio of 101.6% and AUC_0-5d ratio of 101.9%, the 90% confidence interval of C_max was 79.42%-129.92%, and the 90% confidence interval of AUC_0-5d was 85.72%-121.18%. These results suggested that different dosage forms of MIL50 had certain differences in the changes of blood drug concentration in rhesus monkeys.