This paper mainly studies the mechanical properties and microstructure of polyurea coatings (SPUA) through the experiment of dry-wet circulation. The influence of different curing time of SPUA coating before and after the dry cycle of the mechanical properties and surface morphology changes were researched. Use the alternating temperature and low bending tests to research,the variation of temperature changes to the SPUA of different curing time. The result of the dry-wet circulation experiment shows that the tensile strength of cured 1d, 3d and 7d SPUA coating after 30d dry-wet circulation increased 9.6%、19.2% and 44.7% respectively, the tear strength increased 3.2%、5.6% and 47.3% respectively. The microstructure research shows the 7d cured SPUA coating after 30 times dry-wet circulation will reduce the holes and narrow the hole diameter in a certain degree. The temperature change experimental results show that during -20 ～50 alternating temperature process, the tensile strength of the coating appears to increase, 3d and 7d cured SPUA coating after 40d temperature alternating tensile strength changing rate is -14.2% and 9.8% respectively. Low-temperature bending test shows that the SPUA coating will not appear any cracks cracking phenomena after placed the coating in （-20+2 ）for 168h.