Abstract: Test data generation is a complicated problem and its method and technique are not mature.According to the test target,which achieves statement coverage,this paper proposes the largest steady genetic algorithm (LSGA).It considers the steady of GA and this paper proposes the"the neighbor first "principle and" nearby-path numbering"principle when fitness function is built and path is numbered.It can generate the minimal test suite to meet the test target and its performance is superior to GA.