Abstract: In order to study the changing laws of the strength and mechanical properties of paste filling body with age, the concrete proportion of the paste filling body and the curing environment on the basis of the field were considered, the friction angle and cohesion of the specimen were calculated by using the site coring and the tensile strength and uniaxial compressive strength, and the regression analysis was carried out. The results showed that the internal friction angle of the filling material was about 24° to 36°, and the correlation was weak with the age. The tensile strength, uniaxial compressive strength, cohesion showed the property increased with the increase of the age and finally maintained at a stable value, and the initial strength developed rapidly, and then the growth rate was gentle. However, because the underground filling body is in a certain stress environment, it has a certain compaction effect on the filling body, and the strength is higher than that of the sample prepared in the laboratory all the time.