Abstract: Stiffness confinement method (SCM) can effectively alleviate the stiffness in the neutron kinetics equation, and can use larger time steps to obtain the same calculation accuracy and improve the computational efficiency. The existing SCM is mainly used to solve two-group transient neutron diffusion equation. In this paper, the SCM was employed to solve the multi-group transient neutron transportation equation. On the basis of the original method of characteristics (MOC) program PEACH, the transient function was added and the PEACH-K program was developed. Based on the latest published OECD/NEA C5G7-TD benchmark, the numerical result of PEACH-K program was verified. The results show that the PEACH-K program has both high computing precision and good numerical stability.