Abstract:The flower bud differentiation process of Rosa persica lasted for about 30 days from bract promordium differentiation in late March to carpel promordium formation in late Ap ril. The p rocess could be divided into six phases: before differentiation, bract differentiation phase, sepal differentiation phase, petal differentiation phase, stamen differentiation phase and pistil differentiation phase. Of them one time was occurred in differentiation of sepal primordium, and itmight be the reason of forming the simple layer of sepal. An larges of each floral promordium originated in peripheral zone cells of floralmeristem . The increase of cell number and diameter of apical pointwas higher in both extension phase and carpel differentiation phase.