Influence, parameters and model of a 1.2m(3) upflow anaerobic sludge blanket (UASB) reactor were studied, which was operated at low operating parameters of 200mgCOD.L-1. The secondary start-up, operation and kinetics parameters of substrate degradation of the UASB reactor were demonstrated. This reactor was started with sludge loading rate (SLR) of 0.06kgCOD/ kg(-1)VSS.d(-1) and organic loading rate (OLR) 2.4kgCOD.m(-3).d(-1). The start-up is completed basically within 5 days when start-up with granular sludge as seed at temperature about 20 degrees C. The reactor was operated under SLR from 0.025kgCOD.kg(-1) VSS.d(-1) to 0.10kgCOD.kg(-1) VSS.d(-1) OLR from 0.5kgCOD.m(-3).d(-1) to 3.5kgCOD.m(-3).d(-1), liquid upflow velocity from 1.4 to 1.7m.h(-1) and hydraulic retention time (HRT) from 3.0h to 2.5h at temperature in the range from 32 degrees C to 5 degrees C, for six months. The COD removal efficiency was from 40% to 80%. The strength of the UASB reactor must be more than 100mgCOD.L-1, otherwise a dense sludge bed could not be established in the bottom of the reactor. The declining growth rate constants (K-2) of 6.0 x 10(-5) L.mg(-1)VSS.d(-1), 5.0 x 10(-5) L.mg(-1) VSS.d(-1), 2.1 x 10(-5) L.mg(-1) VSS.d(-1) and 2.0 x 10(-5) L.mg(-1)VSS.d(-1) were obtained by mode Grau at the average temperature of 28.5 degrees C, 19.5 degrees C, 11 degrees C and 6 degrees C, respectively.