The utility model provides mobile capacity detection equipment for an energy storage system and is applied to the technical field of energy storage battery capacity detection. The mobile capacity detection equipment for the energy storage system comprises a grid-connected current transformer PCS communication device, a battery management system BMS communication device, battery set string detection devices, a monitoring terminal, a storage battery, a rack and mobile mechanisms, wherein the PCS communication device comprises an Ethernet interface used for connecting a PCS, the BMS communication device comprises a controller area network (CAN) bus interface used for connecting a BMS, each battery set string detection device comprises alligator clip terminals used for connecting output copper bars of a battery string set and an opening type Hall current sensor used for connecting the output copper bars of the battery set string, the monitoring terminal is connected with the PCS communication device, the BMS communication device and the battery set string detection devices via CAN buses, the storage battery is respectively connected with the monitoring terminal, the PCS communication device, the BMS communication device and the battery set string detection devices, the rack comprises at least an element cell, and the mobile mechanisms comprise supporting shafts and rolling wheels. According to the mobile capacity detection equipment for the energy storage system, capacity tests of the energy storage system can be performed, the flexibility is good, the installation and the dismounting are convenient, the equipment can be freely moved, and convenience is brought to the capacity tests of the energy storage system.