Effects of solidification structure and solidified rate on structural morphology, interfacial temperature and phase constituent of Cu-55Sn hypo-peritectic alloy have been investigated with directional solidification rate in the range of 0. 5-100μm. The results show that directional solidified phase constituent is composed of primary ε phase, peritectic rj phase and eutectic （η+Sn） phase. Bulky peritectic rj phase is embedded in primary e phase in the directional solidification Cu-55Sn hypo-eutectic alloy with directionally solidified rate in the range of 0. 5μm/s while with solidified rate more than 5 μm, the solidification structure remains the conventional plate structure, where peritectic rj phase coats primary e phase. Coupled growth in isothermal interface for peritectic rj phase and primary εphase can not be formed because primary e phase is prior phase, which is in accordance with analysis of top-interface temperature growth theory. Major peritectic η phase is directionally formed from the liquid phase during direction solidification process. In addition, with increasing in cooling rate and decreasing in solidification time, peritectic rj phase content is firstly increased then decreased, and the peak content of the peritectic rj phase can be observed with the directional solidification rate of about 10 μm.