Abstract: Network intrusion detection technology based on artificial neural network is an important research direction in intrusion detection area. This paper proposes a semi-supervised GHSOM(growing hierarchical self-organizing maps) neural network algorithm, in which the clustering process of large amount of unlabeled data is conducted by small amount of labeled data. On the one hand, the idea of semi-supervised cop-kmeans algorithm is introduced into the unsupervised GHSOM algorithm, and the problem on returning no result is solved in the semi-supervised GHSOM algorithm. On the other hand, the concept of neural entropy is proposed and used as the judgment condition of the neural network growth to improve precision of division of subnets of the neural network. Besides, the labeled data are also used to determine the intrusion type of nerve cells automatically. The network intrusion detection experiment results based on KDD Cup 1999 data set and the data set collected in LAN both show that the total detection rate of the network intrusion detection system through employing semi-supervised GHSOM algorithm is higher than the network detection rate of the intrusion detection system through employing unsupervised GHSOM algorithm.