In order to investigate the influence of reinforced bar lap splices on the flexural performance of reinforced concrete beams， and verify whether the existing lap length factor can meet the limit requirements of the serviceability limit state of concrete structure design code （GB50010—2010）， taking the lap length and lap percentage as variables， the flexural behavior of 16 reinforced concrete simply supported beams with lap splices under two-point concentrated load was tested. The development of cracks， crack width， crack spacing， failure pattern， flexural bearing capacity， and mid-span deflection of the specimen were observed. The test results show that the lap percentage and lap length have a great influence on the bearing capacity and deformation of the test beams， and the mid-span deflection values of the test beams all meet the limit requirements under the service state load. However， the crack width of the beams with a smaller lap length is difficult to meet. Based on the test data and considering the two parameters of lap percentage and lap length， the relationship between the maximum crack width of beams with lap splices and the maximum crack width of beams without lap splices is given， and the suggested value of the lap length factors is put forward. Based on this， the rationality of the Chinese concrete structure design code and the American ACI 318 code is discussed.