Automatic generation of testing data is an important means for improving the efficiency of software testing. Focusing on the engineering practice of software testing, a fast automatic method is proposed to improve the efficiency of testing data generation.(1) A key-point path expression method is proposed to calculate the number of theoretical paths, and find the covered paths' neighbors;(2) Brief instrumented program is executed to get some testing data by using the testing data generated from random algorithm;(3) The theoretical paths are divided into three parts:Easy-Cover paths, hard-cover paths and infeasible paths;(4) According to the information of covered paths and their testing data, the data of hard-cover paths will be generated by genetic algorithm. Simulation experimental results show that the proposed method is efficient.