The semantic satiation effect refers to the subjective and temporary loss of the meaning to repeatedly perceived or produced word. Using a modified speeded category matching paradigm, the present study investigated the modulatory effect of words’ emotional valence on the time course of semantic satiation. With 24 adult participants, Experiment 1 found that, reaction times in the repeated condition were significantly shorter than those in the nonrepeated condition during the first time period (trials 2-4), whereas no significant difference was found during the second time period (trials 5-7) and the third time period (trials 8-10). These results demonstrated that, the above-mentioned paradigm could be used to successfully induce the semantic satiation effect. In Experiment 2, seventy-two adult participants were randomly assigned to three groups (24 per group) who were administered the paradigm using either positive or neutral or negative words. Results showed that, the semantic satiation effect appeared in later trials (trials 8-10) for positive words, and in middle trials (trials 5-7) for neutral words; while no significant semantic satiation effect was found for negative words. Results are discussed in terms of the depth of processing and evolutionary significance of emotional valence of stimuli (including words). Our findings suggest that the emotional valence of the materials should be considered in future studies of the semantic satiation effect.