The glass transition temperatures T-g of butyl acrylate-methyl methacrylate copolymers obtained by free radical polymerization in 3 and 5 mol/L benzene solution have been measured using differential scanning calorimetry (DSC) and the values have been correlated using Johnston's equation with inter-intramolecular copolymer structure. From the data calculated with copolymer prepared at low conversion, the variation of glass transition temperature with copolymer conversion has been theoretically predicted.