In order to evaluate the process and the effect of straw fermentation at low temperature scientifically and accurately, this paper uses projection pursuit method to evaluate the composting quality of corn straw and fecal water at different stages of low temperature fermentation. The results showed that: with the extension of fermentation time, the compost temperature, the content of potassium oxide and total organic matter first increased and then decreased, and the content of phosphorus pentoxide first increased and then decreased and then increased. As a whole, the content of total nitrogen and weight loss increased, and the content of C/N and water decreased. Among them, C/N decreased to 19.83 after 30 days fermentation, and compost reached the requirement of returning to the field. The result of using projection pursuit model to evaluate the fermentation quality of compost in different period showed that, the comprehensive quality of composting fermentation gradually improved with the extension of fermentation time, and the fermentation quality of compost was the highest on the 30 th day, and its function projection value reached 2.432 3. This study provides a feasible technical reference for the absorption of straw and manure pollution in the alpine region.