Black-Scholes option pricing equation is one of the biggest achievements in modem financial theory.In this paper,we studied the partial integro-differential equation with jump-difiusion process proposed Merton.The discretization of spatial differential operators is by finite difference method.In view of the non-local property of the spatial integral operator,we use explicit time discretization for reducing the compute cost.We further derived the variable step-size IMEX-BDF2 method for solving Merton jump-difEusion model.Numerical e...