Abstract: The multiplicative Monod and non-competitive Monod equation were integrated with theoretical equations determined by stoichiometry and bioenergetics to analysis the simultaneous denitrification and methanogenesis ( SDM) process． Batch experiment was used to obtain the model parameters with sodium acetate as the electron donor and anaerobic granular sludge as seed sludge． The degradation and competition of substrate as well as the inhibitory effect of N-oxides on methanogenesis in the SDM process could be well described using the above models． Furthermore，the cumulative gas production and changes in biomass of each microbial community were predicted． Parametric sensitivity analysis indicated that km，a ，k m，NO3 and km，NO2 were sensitivity factor for methanogenesis，denitratation and denitritation process and their the values were 0. 098 h － 1 ，0. 0824 h － 1 and 0. 0695 h － 1 ，respectively． The results suggested that the maximum specific substrate utilization rate had the most significant effect on the substrate degradation process．