Abstract: A suction catheter assembly is disclosed, which includes a manifold member, an engaging structure, a suction catheter, and a controller. The controller includes a housing, an elastic member, a hollow valve body, an actuating piston, and a cap. The housing has an inlet portion and an outlet portion. The housing has a sealed portion formed on one end thereof. The actuating piston projects through the hollow valve body and abuts to the cap and the elastic member on opposite ends. When the hollow valve body is at closed position, fluid flow is cut off between the inlet and outlet portions. When the hollow valve body is at open position, the fluid flow is allowed. The suction catheter assembly has better air tightness.