The invention provides a variable valve mechanism capable of realizing 2/4 stroke interchange. The variable valve mechanism comprises a cam, two rocker arms, two linear reciprocating devices and a valve, wherein the cam is provided with two types of lines, the two rocker arms respectively correspond to the two type of lines, the two linear reciprocating devices are respectively used for driving the two rocker arms, and the valve is provided with a pre-tightening spring. The magnitude and the direction of the acting force of the two linear reciprocating devices on the two rocker arms are respectively adjusted, so that the variable 2/4 stroke and variable valve lift can be changed. The system does not need to be operated under each working cycle, and the parameters can be adjusted only underthe working condition that the valve movement rule needs to be changed, so that the cost of the valve can be obviously reduced on the basis that the movement of the valve is flexible and variable, the service life of components can be prolonged, and engineering application of the variable valve technology is facilitated.