This paper deals with simulation and genetic algorithm (GA) based test generation for sequential circuits. We proposed a new sequential depth measure called sequential element reachability, which may be used as one of parameters of GA. For fitness functions, we proposed a new dynamic testability measure, which can be evaluated in parallel for multiple individuals. The test generation is divided to three sub-problems: initialization, test vector generation for a group of faults and test sequence generation for a target fault. Using ISCAS89 benchmarks, the experiment results of GA were given.