Sentiment analysis is an important field of study in natural language processing. In the massive data and irregular data, sentiment classification with high accuracy is a major challenge in sentiment analysis. To address this problem, a novel maximum entropy-PLSA model is proposed. In this model, we first use the probabilistic latent semantic analysis to extract the seed emotion words from the Wikipedia and the training corpus. Then features are extracted from these seed emotion words, which are the input of the maximum entropy model for training the maximum entropy model. The test set is processed similarly into the maximum entropy model for emotional classification. Meanwhile, the training set and the test set are divided by the K-fold method. The maximum entropy classification based on probabilistic latent semantic analysis uses important emotional classification features to classify words, such as the relevance of words and parts of speech in the context, the relevance with degree adverbs, the similarity with the benchmark emotional words and so on. The experiments prove that the classification method proposed by this paper outperforms the compared methods.