The invention provides a method and a device for accelerating a string matching algorithm. The method comprises the steps of: constructing a basic transformational rule and a cross transformational rule; determining states Sc1 and Sc2 in a state cache register according to a cache strategy function; judging whether a current state Si in the basic transformational rule and the n-step cross transformational rule exists in a transformational rule which receives a current character C; and transforming the character C according to the corresponding transformational rule. According to the method and the device, through additional arrangement of the status cache component and a gating circuit, such as a register block and a multiplexer, the transformational rule is dynamically generated in a string matching process, the acceleration of the string matching algorithm is realized, meanwhile a large number of transformational rules needing to be stored in the conventional string matching algorithm can be eliminated, the scale for generation of state machines is reduced and the execution speed of the string matching algorithm is accelerated.