Abstract: Based on the flexural static loading test of six concrete beams，the crack distribution and development of CFRP － PCPs ( carbon fiber reinforced plastics prestressed concrete prisms) composites reinforced concrete beams under service load were researched． Considering the influence of CFRP － PCPs composites reinforcement，the calculation methods of maximum crack width and mean crack spacing of concrete beams with CFRP － PCPs composites reinforcement in current Chinese design code for concrete structures were modified． Whose results were compared with experimental results，showing a better agreement between test values and the calculated values given by the modified formulas．