The utility model discloses a flow channel conversion control system. The system comprises a slurry filtering device, communicating pipes, control valves, upright posts and a central control system, wherein the central control system controls actions of the control valves; and the slurry filtering device and the upright posts are communicated with the control valves through the communicating pipes. By the system, due to conversion and control of slurry flow channels, continuous cycle operation of borehole slurry is realized; and therefore, stable borehole pressure is continuously kept, an annular east-circulating device (ECD) value of the borehole is effectively controlled, a stable well wall and a good borehole cleaning effect are kept, collapse and formation of a slant section cutting bed are prevented, and collapse, blockage, leakage, blowout and other complex conditions are avoided. The device is simple, has a small volume and does not occupy a large area of an operating platform, a normal operating environment is kept, particularly the control system can be centralized in a container of the system after being detached, and the control system is convenient to mount and detach, which is important for simple operation of an offshore drilling platform.