Abstract: By introducing a discount effect into a biomass growth and consumption model, comparisons and analysis could be made of the strategies herdsmen might take in the late grassland contract stage. The study showed that with a positive discount rate, herdsmen would take moderate grazing intensity in the contract but in order to have optimal economic income they would graze as heavily as they could at the end of the contract. Compared with not having a discount rate, the overgrazing starting time in this strategy is earlier and the extent is positively related to the discount rate. Having experienced rapid economic development for more than twenty years, discount rates in china are at a relatively high level. To prevent devastating overgrazing, the contract should be redesigned to vary the discount rate before the deadline with herdsmen.