A preparation process of 3-chloro-5-nitrotoluene is provided in mild conditions. It is a process for preparing 3-chloro-5-nitrotoluene, which involves the steps of reacting 2-methyl-4-nitroaniline with a chlorinating agent such as 5-butyl hypochlorite in a neutral condition to obtain 2-chloro-4-nitro-6-methylaniline and deaminating the 2-chloro-4-nitro-6-methylaniline to obtain 3-chloro-5-nitrotoluene.