Cycloaddition reaction HN₃ + NH₂CN → 5-AT has been theoretically investigated by B3LYP, QCISD and MP2 methods with 6-311+G^*basis set. The solvent effects on the geometries, reaction path properties, energies, thermodynamic, and kinetic characters in four solvents (carbon tetrachloride, dimethylsulfoxide, aceton, and water) have been studied by using self-consistent reaction field (SCRF) approach with the polarizable continuum model (PCM). Results show that effects of solvent on the geometric characters and reaction path properties are negligible. The equilibrium constant in dimethylsulfoxide solvent is the largest, so the reaction easier occurred spontaneously in dimethylsulfoxide solvent thermodynamically. The rate constant in the solvents is smaller kinetically than that in gas phase, and 300 to 350 K is the most feasible temperature to the reaction.