The structural, magnetic, and transport properties of Pr5/8Ca3/8MnO3 single crystals with a phase-separated characteristic were systematically studied. One steplike charge-ordered antiferromagnetic-ferromagnetic transition was found below 60K when a magnetic field of only several teslas was applied, and the step in the M-H curve became ultrasharp below 4.2K. Here, the given charge/orbital ordering and spin structure indicated that the energy difference between ferromagnetic and charge ordering was small for Pr5/8Ca3/8MnO3. According to the model of spin and orbital coupling, the steps should be the result of spin reorientation under the magnetic field. Above 10K, however, the step was not sharp, which was caused by thermal fluctuation and then affects the fluctuation rate of orbit.