Research into the effect of interest consistently indicated that interest positively related to students' achievement; however, the mechanism through which it affected the learning result remained an open question. This study intended to examine how learning strategies mediated the relationship between interest and achievement in the domain of history learning. Biggs Learning Process Questionnaire, which distinguishes between the surface and deep-level learning strategies, was adopted to describe students' learning process. Structural equation modelling and the distribution of products test were used to evaluate the mediating effect. Based on available resources, the participants were seventh grade students in China. Analyses revealed that the surface-learning strategy served as a mediator, but the deep-learning strategy did not play the same role.