Abstract: Grouting is an effective method to solve the mine water disaster．In order to better study the sedimentary pressure characteristics and water blocking effect of the slurry in the process of dynamic water grouting，experimental study of dynamic water grouting to the coal and rock fissures was carried out by using the self－designed hydrodynamic comprehensive test platform，analysis was made on the sedimentary pressure characteristics of the slurry in the coal and rock fissures under the conditions of different water－cement ratio and grouting pressure，a method for evaluating the dynamic water grouting effect was put forward．The results showed that the sedimentary pressure curve of the slurry could be divided into three types，when the curve was in plain－type distribution，the water blocking effect by grouting was the best，when the curve was in peak－type distribution，the water blocking effect by grouting was the second，and when the curve was in bench－type distribution，the water blocking effect by grouting was bad．