Abstract: RP-HPLC was applied to the determination of residual amount of methyl methacrylate (MMA) monomer in intraocular lens (IOL) made of polymethyl methacrylate (PMMA) or made of hydrophilic methacrylate (HMA). Soxhlet′s extraction was used for the separation of MMA monomer; isopropanol was selected as extraction solvent for IOL sample of PMMA and acetonitrile was selected as extraction solvent for IOL sample of HMA. The extracts were concentrated by rotary evaporator, and the concentrate was used for RP-HPLC analysis. Waters C18 column was used as stationary phase and acetonitrile-H2O mixture (30+70) was used as mobile phase in the separation. Ultraviolet detector at 220 nm was adopted in the determination. Linear relationship between values of peak area and mass concentration of MMA was obtained in the range of 0.33-42.08 mg·L-1 with detection limit (3S/N) 0.02 mg·L-1. Values of recovery were ranged from 98.5% to 106.2%, and RSD′s (n=6) of intra-day and inter-day found were 0.72% and 0.92% respectively.