Abstract: In the paper, a way of amending λ was introduced to solve the point reactor neutron kinetics equations so that the numerical solution of singlegroup delayed neutron model is closed to that of six groups delayed neutron model when a positive stepchanged reactivity was introduced. Based on this, a resolution was gotten for single group delayed neutron model. The analysis shows that when λ is amended the resolution of single group delayed neutron model is approximately equal to the numerical solution of sixgroups delayed neutron model, which meets engineering accuracy. At the same time, the course of equations’ resolving is simple, avoiding the stiffness of numerical computation. In this way, the fast calculation can be achieved.