Previous studies have found that emotion has significant influence on the learning of foreign language vocabulary and textual comprehension. However, little attention has been given to the effect of induced emotion on grammar learning. This research examined the influence of positive induced emotion on the learning of Japanese grammatical rules among a group of learners with Chinese as their native language, using a semi-artificial language (i.e. Chipanese), which combines the grammatical rules of Japanese and the vocabulary of Chinese. Music was used to invoke positive emotional conditions in participants. Participants were required to learn Chipanese sentences in a training session through practice and then a grammaticality judgment task was administered to measure learning outcomes. We found that participants in positive emotional states performed less accurately and efficiently than those in the control group. Positive emotion had an inhibitory effect on the learning of foreign language grammar. The findings suggest that the protocol is effective in identifying the effect of positive induced emotion on grammar learning. The implications of this experimental paradigm for investigating foreign language learning are discussed.