Abstract: A direct copolymerisation process was used to prepare lactic acid and glycolic acid copolymer (PLGA). Rheological behavior of PLGA melt was tested using cone and plate. It was found that PLGA melt was paeudoplasic fluid,and non Newtonian index value of PLGA melt was bigger than that of PLLA melt, which indicated that the dependence of the PLGA viscosity on shear rate was less; Under the same shear rate, the flow activation energy of PLGA was higher than that of PLLA, which indicated that the viscosity of PLGA was more sensitive to temperature.