This paper proposed an enhancement start-up strategy for accelerating the start-up of a membrane bioreactor (MBR) for treating micro-polluted surface water under low temperature. The surface water ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) were firstly enriched in a culture apparatus, and they were further acclimated to surface water through an MBR. Then the prepared mixed liquor obtained from the culture apparatus with natural start-up was introduced into new MBRs fed with reservoir water, and the start-up behaviors were discussed. Results indicated that the enrichment of AOB and NOB lasted for 27 days at 7.3 °C and the acclimation (at 5.9 °C) was completed within 3 days. After inoculating with the prepared mixed liquor, the start-up of the MBR was accomplished within 10 days at 9 °C with the flux of 11 L m–2h–1 (LMH); while operated at lower initial flux (5.5 LMH) and relatively higher temperature (11 °C), it took 3 days for start-up of the MBR. However, the MBRs exhibited stable but not satisfactory organic removals under low temperature during the start-up.