To shorten the start-up period of UASB process for the low temperature municipal wastewater treatment, two lab-scale UASB reactors were employed to study the feasibility of enhanced start-up with addition of waterworks wastewater to raw water. Also the operation and biomass characteristics were investigated with comparison of conventional start-up mode. The results show that, under the water temperature of 15℃ and the initial organic loading rate (OLR) of 0.25 kgCOD/(m3·d), the UASB system can get stable condition with both the OLR escalating and enhanced mode, and the start-up period is approximate 120 days and 95 days respectively. Throughout the experiment the enhanced start-up processes preferable adaptability, which shorten 30days to achieve the OLR of 4 kgCOD/(m3·d), and higher COD removal as well as biomass growth rate (0.029 g VSS/d versus 0.043 g VSS/d) correspondingly. Compared to conventional mode, the mean diameter of granular sludge is larger and 2 mm granular sludge can be formed within 95 days by enhanced mode. The experimental results demonstrate that adding waterworks wastewater can shorten the start-up time and enhance granulation, which in turn leads to improvement in organics removal efficiency and stability of the UASB system for low temperature municipal wastewater treatment.