There are many cascaded power electronic devices and closed-loop control load converters in supercapacitor/lithium powered ships. They can all be regarded as constant power load (CPL). Their negative impedance characteristics will amplify the instability of the system and even make the entire system unable to work normally. To solve the problem, this paper proposes a novel finite-time controller. First, a mathematical model of the dual-electric ship's DC electric propulsion system is constructed and the proportional/integral droop control method for hybrid power generation units is introduced. Then, based on finite-time control theory, a new finite-time controller with hyperbolic tangent function is designed, in which various disturbances are observed through the designed finite-time observer, and compensated for by the controller. Finally, simulation models and experimental platforms are built. Their results show that the proposed controller can improve the large-signal stability of the system with CPL while ensuring the frequency division response of the hybrid power generation unit to bus voltage fluctuations. This work is supported by the National Natural Science Foundation of China (No. 51709028 and No. 51979021).