Red Blood CELLs (RBCs) are the main CELLs in human blood, with a main role in the mechanical properties of blood as a fluid. Several methods have been improved to simulate the mechanical behavior of RBC in micro-capillaries. Since, in microscopic scales, using discrete models is more preferred than continuum methods, the Moving PARTICLE Semi-Implicit method (MPS), which is a recent innovative PARTICLE based method, can simulate micro-fluidic flows based on Navier-Stokes equations. Although, by recent developments, the MPS method has turned into a considerable tool for modeling blood flow in micro meter dimensions, some problems, such as a commitment to use small time step sizes, still restrict the method for large models and also for long time simulations. A new modified semi-implicit algorithm is developed and implemented on RBC motion through microvessels, in order to reduce calculation time by more than a factor of twenty, while the error of position and velocity remains constant. A two-dimensional, parallel plate, fluid flow is simulated based on the proposed method, and the effect of the calculation time decrement is evaluated. Findings indicate a reduction of 90 percent in simulation time compared to previous studies with the same results. This significant developed method could be applied to RBC interaction within micro-capillaries and constricted zones in blood flow.