The invention provides a stepless variable-valve-lift mechanism. The stepless variable-valve-lift mechanism comprises a driving cam, a rocker arm, air valves, tappets and a rotating driving device, wherein each air valve comprises an air valve lifter, the air valves and the tappets are located on the same side of the rocker arm and located at two ends of the rocker arm, top ends of the tappets abut against the rocker arm, the driving cam is located on the other side of the rocker arm, and the rotating driving device is connected with the tappets and is used for driving the tappets to rotate, so that included angles formed by axes of the tappets and axes of the air valve lifters are changed. The stepless variable-valve-lift mechanism is ingenious in design, simple in structure, easy to implement, low in cost and capable of being widely used for high-grade, middle-grade and low-grade cars.