Low temperature and high salinity can strongly inhibit metabolic activities of the microbial population, resulting in low efficiency of biological wastewater treatment. Using 70 g.L-1 NaCl pickle mustard wastewater as influent, three pilot-scale sequencing batch biofilm reactors (SBBRs), subjected to temperature downshifts and fluctuation ranging from 30 ± 4°C to 10 ± 4°C, were conducted over 200 days. Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR–DGGE) was used to reveal the microbial community structure succession in reactors. Results showed that when the temperature was 10 ± 4°C, the COD removal efficiencies of SBBRs (1, 2 and 3 kg COD m-3 d-1 organic loading rate), were 91.6% (σ = 0.87), 87.84% (σ = 0.92) and 83.34 % (σ = 0.85), respectively. Compared with the average removal efficiencies when the reactors operated at 30 ± 4°C, the efficiency reductions of 1, 2 and 3 kg COD m-3 d-1 reactors were 4.47%, 4.58% and 4.57%. As the temperature decreased, microbial population diversity did not change remarkably. However, the microbial structure changed significantly, bacteria which had strong adhesion and a wide growth temperature range were competitive. At low temperature, the predominant species were Thalassolituus oleivorans, Halotalea alkalilenta and Kangiella koreensis, which were all related to pollutant-degrading halophilic bacteria.