The invention discloses thermal insulation mortar. The thermal insulation mortar is prepared from, by weight, 45-60 parts of cement, 5-10 parts of closed-cell perlite, 10-15 parts of pulverized fuel ash microspheres, 3-7 parts of carbon nanotubes, 1-3 parts of bamboo fibers, 3-6 parts of nanometer silicon aerosol, 2-4 parts of phenol and 1-3 parts of sodium hexametaphosphate. According to the thermal insulation mortar, the cement, the closed-cell perlite, the pulverized fuel ash microspheres, the carbon nanotubes, the bamboo fibers, the nanometer silicon aerosol, the phenol and the sodium hexametaphosphate serve as raw materials and are reasonably matched in proportion, all the ingredients interact and affect one another, and the strength of the prepared thermal insulation mortar is improved.