A mathematical model of an ecosystem is presented in this article that consists of four species S1, S2, S3 and S4. In this paper we have considered S2 be the predator of prey S1 where as S2 is commensal to the host S3 and S3, S4 are mutual pair. Pairs S2, S4 and S1, S3 are neutral. The local and global stability of the deterministic model together with its stochastic analysis have been carried out around the co-existent state. Bionomic equilibrium of the system is derived. Further numerical simulations are performed to validate the results. © 2014 Institute of Advanced Scientific Research.