Non-free-cutting is an effect which affects the mechanism of micro cutting greatly. The influence of cutting intervene between elementary cutting tool on chip flow direction was analyzed, and chip flow intervene of the rounded-edge tool was mathematically modeled aims at the increase of cutting intervene caused by chip flow in the rounded-edge of micro cutting tool. Furthermore, chip flow direction, equivalent cutting edge and chip flow angle were deduced with Stabler rule and minimal energy dispersion principle respectively. Those above parameters were numerical predicted under different feed rate and cutting depth, and the prediction results can be used for the evaluation and improvement of micro-cutting status, as well as the optimization of cutting regimes.