Rosette form control in superimposition of different dot color was studied. Rosette formation conditions and cyclical changes rules were discussed. A method to precisely control rosette form by adjusting horizontal position of color plate was obtained. The result showed that the necessary condition for dot overlap to form rosettes is the same screening lines and screen angular difference of 30 degrees; hollow and center rosettes conversion can be realized by moving color plate along the direction of screen angle half dot cycle; precise control of rosettes can be realized by adjusting color plate direction along the screen angle direction converted to horizontal or vertical direction.