OBJECTIVE: To study the suitable age for intraocular lens (IOL) implantation in children. METHODS: 240 (240 eyes) normal children aged 3-13 years old were selected. Their corneal refraction, anterior chamber depth, lens thickness and ocular axial length were measured with Roden-Stock Keratometer C-MES and Eyescan Model 55 separately. RESULTS: The corneal refraction of 3-year-old children, the anterior chamber depth and lens thickness after 5 years old, and the ocular axial length after 9 years old approach the adult magnitude. CONCLUSIONS: A 3-year-old child has been qualified with IOL implantation, the child younger than 9 years old should be implanted with a normal adult IOL and then corrected with glasses, and a child after 10 years old should be directly implanted with a proper dioptric IOL.