Aiming at the decision-making problem of process route in a CAPP system, an algorithm based on the genetic algorithm for optimization of process route was illustrated by an example. A machined part was divided into some feature cells machining chains of that were generated by reverse design. Then the preference sequence of feature cells was determined and the objective function was built. A checking program was designed to ensure the validity of chromosomes. The fitness function was built based on the objective function. The operator algorithms of replication, crossover and mutation were designed and the process route were optimized using the genetic algorithm. At last, the feasibility and effectiveness were verified by an example.