In current engineering practice, the phase of the short-circuit current provided by a grid-connected energy storage plant is affected by the pre-fault status of charging and discharging. When energy storage encounters a fault in the transmission line during charging, the phase difference is likely to be large between the short-circuit current it provides and the short-circuit current provided by the grid on the other side of the line, leading to a risk of no-trip failure in traditional current differential protection (CDP). To address the above problems, this paper proposes a modified current differential protection criterion based on adaptive phase compensation (MCDP). By judging the state of energy storage charging and discharging state as well as the presence of negative sequence currents, current phases on both sides of the line will be compensated at different angles, so as to reduce the phase difference and improve the sensitivity of the protection without reducing the reliability. The performance test of the MCDP is carried out through PSCAD simulation. The results show that the MCDP has good performance under different fault conditions and ability to resist fault resistance.