Polymers of Glycidyl Methacrylate (PGMA) were prepared by using dicumyl peroxide (DCP) as initiator at 160℃, then they were characterized by infrared spectroscope (FT-IR) and thermal gravimetric analysis (TGA). The average molecular weight of PGMA was determined with gel permeation chromatograph (GPC), the intrinsic viscosity of three PGMA with different amounts of DCP was measured with viscosimetry, then K and α values in Mark-Houwink equation of polymers were determined. The experimental results show that PGMA of a large molecular weight was formed during the course of GMA polymerization via heat initiation, and the polymerization degree of GMA was declined because of addition of DCP. The K and α values of PGMA solution were determined to be K=9.1×10^-4mL/g,α=0.87, which indicates that the molecular chain of GMA is in a stretched state in acetone.