［Objective］To develop a high-performance coatings for the backside of solar thermal mirrors using a self-made blocked polyisocyanate curing agent.［Methods］ The blocked polyisocyanate curings agent was synthesized using aliphatic hexamethylene diisocyanate（HDI）， trimethylolpropane（TMP），and 3，5-dimethylpyrazole as raw materials. A one-component mirror backcoatings was prepared with functional polyester topcoat，and the application performance of this coatingon the back of solar thermal mirrors was studied.［Results］When the ratio of n（—NCO）to n（—OH） was set at 0.8，the coatings met the requirement of rapid curing at 170 ℃ for 3 minutes. The cured paint film exhibited excellent mechanical properties such as pencil hardness，flexibility，impact resistance and abrasion resistance. After 4 000 h of artificial weathering test，the paint film showed no cracking or chalking. After 2 000 h of 5% neutral salt spray test，the paint film displayed no edgecorrosion. Both of the technical requirements for temperature change resistance and heat and humidityresistance of the paint film were met.［Conclusion］ This solar thermal mirror back coating has excellent performance and broad application prospects.