This in-vitro study was done to compare the effect of LED light curing system on polymerization and hardness of two composite resins system. A Total of 40 samples, 20 samples prepared using silorane based – Filtek LS and 20 samples prepared using methacrylate based- Filtek Z350 XT in a plastic molds with diameter of 8 mm and thickness of 3 mm and cured with LED curing light. knoop hardness testing was done using a 50grams load and a dwell time of 15sec and percentage depth of cure is calculated and statistical analysis was performed using Student t- test. Results showed that silorane based composite was found to have better hardness n depth of cure than methacrylate based composite. Top surface have better hardness than bottom surface.