Magnesium matrix composite reinforced with submicron SiC particles was subjected to room temperature deformation. A stepped tensile method was adopted to observe the development of microstructure at different tensile strain state. The microstructure evolution determined by transmission electron microscopy showed that the existence of submicron SiC particles could promote dislocation multiplication as well as impede dislocation motion. Dislocation density around SiC particles increased with the increase of tensile strain. Compared with the matrix alloy, the composite could withstand greater external loads, which can be related to the pinning effect caused by the submicron SiC particles on the movement of grain and twin boundaries. The study of the interface between the submicron SIC particles and matrix in the composite suggested that single submicron SIC particle bonded well with the matrix alloy after tensile process. Initiation of micro-cracks usually generated in the submicron particle dense zone during tensile process, which could lead to the fracture of composite. (C) 2014 Elsevier B.V. All rights reserved.