Objective This study was performed to determine the hematological parameters of 853 normal juvenile cynomolgus monkeys and establish a hematological reference range for laboratory cynomolgus monkeys from 1 to 4 years of age in Guangdong Province. Methods In total, 273 cynomolgus monkeys aged 1-2 years (1≤x<2)(124 females, 149 males), 307 cynomolgus monkeys aged 2-3 years (2≤x<3)(244 females, 63 males), and 273 cynomolgus monkeys aged 3-4 years (3≤x<4)(124 females, 149 males) were randomly selected. Hematological indicators were measured, and subgroups were compared by sex. Results The reference range of normal hematological parameters in various age groups of experimental cynomolgus monkeys was established. In the comparison between male and female animals, the platelet count and 7 other indicators were significantly different in the 1- to 2-year old animals ( P <0. 05 or P <0. 01), the red cell distribution width-standard deviation and 5 other indicators were significantly different in the 2- to 3-year-old animals ( P < 0. 05 or P <0. 01), and the white blood cell count and 11 other indicators were significantly different in the 3- to 4-year-old animals ( P <0. 05 or P <0. 01). Conclusions Juvenile cynomolgus monkeys are still in the developmental stages and their hematological parameters vary greatly at different ages, and obvious differences are present between males and females at the same age. This study provides hematological background data of normal juvenile cynomolgus monkeys, which can serve as a reliable reference for their application in the biomedical field.