Abstract: Objective To address the problems of asynchronous rotational speeds of the left and right motors, uneven distribution of chain tension, and insufficient feed stability of the power head in the dual-motor chain-driven feed system of a roller cone drilling rig. Methods A dual-motor speed-synchronization composite control method based on working condition-adaptive multi-objective particle swarm optimization (MOPSO) is proposed. An equivalent dynamic model of the motor-sprocket-chain-power head system is established, a synchronous compensation loop for dual-motor rotational speed is introduced, and a multi-objective fitness function incorporating speed error, synchronization error, chain tension difference, speed fluctuation and gain penalty term is constructed. The synchronization gain is adaptively optimized according to the error characteristics of different drilling intervals, and simulation verification is conducted with field-measured data. Results The results show that the established model can effectively track the variations of the power head’s speed and displacement. Compared with the scheme without synchronization control, the proposed method reduces the root mean square error (RMSE) of the dual-motor synchronization error by approximately 95% in the main simulation interval, reduces the chain tension difference, maintains the stability of the feed speed, and significantly improves the synchronization performance and operational stability of the system.