Abstract: An interpolation method exploiting both the Markov model and sequential Gaussian co-simulation (COSGSIM) is proposed to solve the instability of cross matrix when determining the weights of the interpolation equation in COSGSIM.According to the hypothesis of screening effect provided by a Markov model, the hard datum to be simulated screens the influence of any other hard data on the soft datum at the same location.Therefore, the instability of cross matrix can be dissolved by preserving only the soft datum that has the same location with the hard datum to be simulated, while ignoring the impact by other soft data when approximating the COSGSIM.Experimental results show that the deviation is small and the simulated result is good.