AIM: To investigate 5-hydroxytryptamine (5-HT) function and 5-HT receptor 2A (5-HT2A) mRNA expression in the formation of lens-induced myopia (LIM). METHODS: Lens-induced myopia construction method was applied to generate myopia on guinea pig right eye (LIM eye). RESULTS: LIM eyes formed significant myopia with longer axial length. 5-HT level in retina, choroids and sclera from LIM eyes was significantly higher than that in control group. 5-HT2A mRNA expression was also significantly up-regulated. CONCLUSION: Refraction lens could induce myopia in guinea pig and 5-HT may play an important role in the formation of myopia by binding with 5-HT2A receptor.