Abstract: Based on the grassland-livestock-atmosphere system analysis, monitoring models for winter drought and heavy snow were established. Some primary factors (such as continuous snow-free days, possible incidence periods, maximum snow depth and continuous snow-covering days) and basic factors (such as the stress-resistance index of livestock and the average depth of mixture grass before winter) are selected in building the models. Grading indexes for the disasters were determined according to appraisal coefficients, livestock's performance and grazing condition. The verifications show that both the monitoring models and the grading indexes could be put to practical use.