The innovation of level control of an offshore three-phase separator is discussed. The control objective is to smooth down the water outflow-rate as much as possible, subject to keeping the water level inside the separator within a permissible range. Based on the current control system (PI control) which seems developed as a level servo control system, a number of new control coefficients are developed using three different cost-effective tuning methods, namely trial-and-error method, butterworth filter design method and IMC method. The simulation results show that all these developments can significantly improve the system performance compared with the current control system. The potential to use some new control structures and advanced control methods are also discussed.