Based on the distributed parallel environment, for one of the nonuniform domain numerical simulation problems of reservoir, the authors give a load-balance model of parallel computing and a zonal parallel algorithm of load-balance using domain decomposition method, so some well and effective solutions which balancly map the nonuniform domain numerical simaulation of reservoir to parallel environment are found. In the study of block oil reservoir numerical simulation parallel software, the practical results show that the zonal parallel algorithm can improve the performance in speedup.