The two phase fluid distribution is mainly dominated by wettability in rocks where the wetting fluid is always contacting with the pore wall.It can be interpreted by 2D NMR method because in the confined pores with internal gradient of magnetic field,the wetting fluid is diffusion restricted,whereas the nonwetting fluid is free of these influences.Digital rock technique can provide high resolution image of the rock core.By filtrating and binary image segmentation,we extract the pore network of the rock which is provided for NMR simulation of wettability characterization.The wetting phase is represented by a thick fluid film contacting the pore wall and the nonwetting fluid is distributing in the rest of the pore.The internal gradient is represented by a uniformed internal magnetic gradient.2D NMR signal is simulated by Monte Carlo Random walk method with DE-CPMG sequence.With inversion method interpreting 2D NMR data,the D-T2 map of the fluid is obtained.The sandstone rock example for simulation is water wetting with oil distributed in the center of the pore network.As the example shows,the relaxation time of oil and water is different and the diffusion coefficient of water is deviated from the intrinsic value.The deviation is caused by the restricted diffusion of wetting phase,whereas the relaxation mechanism of nonwetting fluid is bulk relaxation,the value of which is close to the bulk value.As the example demonstrated,the wettability of the two phase fluid can be interpreted by the 2D NMR simulation method.