The invention discloses a production process of pyrolysis cyanuric acid, comprising: pumping liquid urea at 132-140 DEG C continuously at a flow speed of 5-6 m/s under 5-10 m<3>/h into a roller barrel into which superheated steam at a temperature of 50-500 DEG C under a pressure of 3-4 Mpa under 500-1000 m<3>/h is introduced, polymerizing urea at 250-280 DEG C to generate crude cyanuric acid, refining the crude cyanuric acid from the roller kiln, and then preparing cyanuric acid 98.5-99% in purity. Heat required for melting urea can be saved, energy consumption can be effectively reduced, high-temperature steam produced in byproduct acid production from sulfur is used to provide heat, the defects such as low heat utilization rate of hot air, high coal firing consumption and high post-treatment cost of pollutants are overcome, zero environmental pollution is caused, heat loss is low, material consumption is low, product quality is stable, and product yield is high; operating is facilitated, safety is high, an operating environment is good, labor intensity is low, carbon emission is reduced, environmental pollution is reduced, heat utilization is increased, and product quality is improved.