The application of neural networks in Numerical Control (NC) machine reliability researching is introduced in this paper. Because of small reliability data sample, it is difficult to establish the reliability data distribution model, predict the reliability and allocate the reliability of NC machine. By using the neural networks, the reliability data of NC machine is extended. The reliability data distribution model can be established, the reliability prediction can also be done accurately. It is proved by the instance that the reliability prediction accuracy is improved 57% by the proposed method. The application of neural networks has a good reference to NC machine reliability researching.