Abstract: In order to overcome the disadvantages of the long period, high cost, and high labor, an on-line monitoring and measuring system of the pastes backill b ody in the goaf was self researched and developed and was applied to the monitoring and measuring of the backfill body compression value, stressing and hydration re action.The results could be applied to the evaluation of the backfill effect.The monitoring and measurement, showed that the compression value of the pastes backfill bo dy was 104.3 mm, the compression rate was only about 3.85% and the aggregate mixed rate of the paste was rational.The max stress of the pastes backfill body was 5. 1 MPa and the bending deformation of the overburden strata was small.The hydration temperature of the pastes backfill body could reach 54 °C in max and the hydratio n reaction would be most serious at the second day.The initial strength of the pastes backfill body would be increased quickly and could be favorable to improve the pro duction of the backfill mining coal face.The pastes backfill body would have a good effect to control the overburden strata movement.