In recent years, solar assisted heat pump based heating system has been widely applied in the buildings and greenhouses, but it is little applied and researched in biogas projects. Exergy analysis of solar assisted heat pump based heating system of biogas project was conducted, and the weak links were found in the energy-using process; system status parameters were obtained by solving variable nonlinear optimization problem with Matlab; specific measures and methods of improving system exergy efficiency were proposed and validation experiments were done ;the effect of individual status parameters and equipment performance parameters on system exergy efficiency was also studied. The results showed that optimized system exergy efficiency can increase from 18.44% to 28.99%. The status parameter(storage tank temperature tv) and performance parameters(pump system CCOP(year) and collector efficiency ηcol) have a great influence on system exergy efficiency. The system exergy efficiency can increase by 0.58% with the temperature increasing by 1℃, increase by 5.94% with the CCOP (year) increasing by one unit of value, increase by 0.045% with the collector efficiency ηcol increasing by one percentage point.