Based on the principle of spinning process of micro grooves inside the circular micro heat pipe, the effects of relative position of balls and tool on the formation of micro grooves were investigated in this work. Experimental results showed that the relative position of balls and tool and ball equivalent diameter generally determined the pattern of grooves, including groove width and depth. Micro grooves could be produced when suitable value of D was chosen and the rake face of tool was near to the center of balls. In the experiment, the largest aspect ratio of micro grooves were achieved with the conditions of D= 5.56mm, d=-3.293mm and v=5.08mm/s. And the structural parameters were w=135μm, h=154μm and k=1.141.