Abstract: Parallel Particles Collision in Lennard-Jones Potential was developed on a distributed-memory parallel computer using MPI library. The empirical results has shown the improvement in efficiency. The previous study found some characteristics of the program that seem to work well on a shared-memory architecture. This project developed a parallel particles collision program on shared-memory parallel computer using OpenMP library. The goal of this project is to compare the performance between MPI and OpenMP implementation of parallel particle collision. We compared the execution time of both parallel programs. The empirical results showed that the OpenMP parallel execution has performed better than the MPI parallel execution.รึป่าว