Abstract: In this paper a generalized extension of the block correction technique is developed including formulae for a multiple block(arbitrary number of blocks)correction technique, and the effect of the number of correction blocks on convergence is studied, with the following findings: 1. There is an optimal number of correction blocks for a problem, for which the CPU time is the smallest. 2. As the number of grid points in the calculation domain increases, the optimal number of correction blocks increases. Generally speaking, when the number of grid points between 20×20 and 10×10, double block correction is the best, when the number of grid points is about 30 × 30, triple block correction might be the best, while if the number of grid points is even greater, multiple block correction may be needed to save computer time. 3. Boundary conditions may have a significant influence on the optimal number of blocks. In general, boundary condition problems of the second type may nead more blocks in the correction technique than the first type.