Preparation process for nitroguanidine

The invention discloses a preparation process for a single-compound explosive, i.e., nitroguanidine. In the process, the nitroguanidine is prepared by adopting a nitric acid method. A technical process comprises the following steps of: synthesizing nitroguanidine; controlling the crystallization of the nitroguanidine; washing the nitroguanidine; and drying the nitroguanidine. The process mainly comprises the following steps of: controlling process parameters such as temperature, stirring speed, dripping speed and the like in a crystallizing process; preparing a dilute nitric acid base solution of a proper mass concentration; and dripping a nitroguanidine reaction liquid into the nitric acid base solution for crystallizing, washing and drying to directly obtain a beta crystal form nitroguanidine product of which the purity is higher than 99 percent, the acidity is less than 0.06 percent and the granularity is 4-6 mum and which meets the requirements of a national military standard. Due to the adoption of the preparation process, energy consumption and secondary pollution caused by secondary crystallization due to unqualified granularity, acidity and purity of the crude nitroguanidine in the conventional process are avoided.