Abstract: A system for analyzing a sentence emotion is provided. The system comprises a case repository, an input module, a sentence structure analyzing module, a similarity analyzing module and an emotion detection module. The case repository stores several case sentences and each case sentence comprises at least one major term and is corresponding to at least one emotion annotation. The input module receives an input sentence and the sentence structure analyzing module analyzes a sentence structure of the input sentence. The similarity analyzing module performs a semantic analysis and a syntax analysis according to the sentence structure to obtain a similarity level between the input sentence and each of the case sentences. The emotion detection module detects at least one emotion of the input sentence according to the similarity level between the input sentence and each of the case sentences.