用从头算方法研究了H+HNCO→NH_2+CO的反应机理:首先经过H_2NCO中间体,并为反应的控制步骤.在此基础上,计算了控制步骤的反应途径,沿反应途径的动态学性质和正则变分过渡态理论的速率常数.结果表明,反应存在返回效应和隧道效应,反应途径的曲率对隧道效应影响较大,用变分过渡态方法和小曲率近似方法分别进行校正是有效的. The ab initio method was used to study the reaction mechanism of H + HNCO → NH 2 + CO: H 2 NCO intermediates were firstly passed through and reaction steps were followed. On this basis, the reaction routes of the control steps, the kinetic properties along the reaction route And the rate constants of the theory of regular variation transition state.The results show that the reaction has a return effect and a tunnel effect, and the curvature of the reaction route has a great influence on the tunnel effect. It is effective to separately calibrate the tunneling effect with the variational transition state method and the small curvature approximation method .