Marine current turbines need to operate at sea for a long time, facing a changeable marine environment and harsh working conditions, and are prone to component failures. Therefore, it is necessary to use efficient and reliable pitch technology to achieve unattended, stable, month-long operation corresponding to lunar rhythm, enhance redundancy and reliability, and extend the service life of the turbine. A hydraulic collective pitch system was designed for a 120 kW horizontal-axis marine current turbine, and a pitch angle redundant measurement scheme was proposed to measure the pitch angle directly and indirectly. Pitch control strategies were designed, including pitch-assisted launch, power-staged control, and two-way current energy harvesting, based on marine current reversal determination. A joint simulation was carried out using AMESim and MATLAB/Simulink software, and a sea test was performed based on the test platform. The simulation and sea test results demonstrated that the designed pitch system operates normally, and the pitch strategies can reduce pitch system loss and achieve month-long reliability.