Since the prepressing property of low molar ratio urea formaldehyde resin was not suitable enough for veneer layingup during plywood production, the authors tried to improve it by adding DDS additives. The test result was found that DDS could shorten the prepressing time greatly and the veneers could be assembled more easily. Further experiments were conducted to investigate the effects of concentration of DDS as well as consumption of DDS with RN, a cation surface activator, on prepressing property of the resin. Results showed that the optimum concentration for DDS is between 0.3%～0.5%, while the consumption of DDS is less than 5%,and RN less than 8% which could be adjusted according to production status in different plywood factories.