In the dynamic environment, mobile robot dynamic path planning is a difficult problem to solve. The paper proposesd a method of path planning based on genetic arithmetic. This method utilizes real number coding and adaptive function with definite physical meaning in the dynamic environment so that the real-time operation speed and operation precision can be accelerated and improved respectively. The method makes full use of the available genetic algorithms to solve dynamic path planning problem of mobile robot. Computer simulation experiment shows that, the method has good path planning ability.