Flow structure and mixing characteristics of a micro combustor using a baffle with square multi-holes inducing axial-switching were numerically investigated. The results show the variation of jet merging due to the mutual interaction between adjacent jets in an arrangement of square multi-holes. In the case of the square jet, the mixing efficiency increases as compared with the circular jet because the size of the main recirculation flow is large and rapidly appeared. In particular, high mixing characteristics are obtained in arrays with square holes between 30 and 45 degrees. From the results, it can be applied to the design of a micro combustor by suggesting optimal conditions to improve mixing characteristics.