In order to predict the psychological status of teenagers accurately and quickly and find their psychological problems in time, this paper proposes a BP neural network classification model based on LM algorithm. Compared with BP neural network of steepest descent algorithm, the LM algorithm has better convergence speed and accuracy in the inversion coefficient experiment. In the Chinese text sentiment analysis experiment, the Precision, Recall and F1 values of LM-BP were better than SD-BP. Based on LM-BP model, this paper presents a design scheme of teenagers mental health classification and recognition system. The scheme has good stability, availability and scalability, which lays a technical foundation for the implementation of the system.