Abstract: Aimed at the problem that the back-to-back start of pumped storage units under low head condition is easy to fail due to the improper coordination of speed regulation and excitation parameters, a multi-objective optimization strategy for back-to-back starting of pumped storage units under low head condition based on refined model is proposed. First, considering the nonlinearity of hydraulic actuator, pump turbine, water passing system and synchronous motor, a water machine electric coupling fine model which could simulate the operation state of water turbine, pump, generator and motor of pumped storage unit is established. The influence of water head on back-to-back starting process is analyzed, and the relevant physical laws of starting process are obtained. Aimed at the double objectives of the speed stability time of the towed machine and the speed overshoot of the towed machine, the multi-objective optimization method is used to optimize the segmented opening law, the optimal external file set is obtained, and the optimization results are simulated. The simulation results show that the proposed multi-objective optimization strategy for back-to-back starting can effectively inhibit the tractor from going deep into the S-shaped zone, and the optimization results can provide decision support for the formulation of back-to-back starting control strategy of large pumped storage units.