Based on the adhesion issue of polyaspartic polyurea primer，influence factors affecting coating adhesion were analyzed and discussed. Polyurea primer coating with differentthicknesses on standard low-carbon steel plates were prepared through spraying，and the coating adhesion was tested. Based on the qualitative analysis of porosity status and the electrochemical quantitative analysis of porosity，the relationship between porosity and adhesion was explored，and the effect mechanism of internal stress of coating on adhesion under high coating thickness was analyzed. The results showed that the thickness of polyaspartic polyurea primer coating had a significant impact on adhesion，and an appropriatecoating thickness range contributed to increase adhesion. Different coating thicknesses wouldlead to different porosity，the adhesion was inversely proportional to porosity in the low coating thickness range. As the coating thickness increased to a certain extent，the influence of porosity on coating adhesion weakened，and the influence of internal stress on adhesion dominated，resulting in the decrease of coating adhesion under high coating thickness.