Taking roof destruction of large height mining face end area of Pingshu Mine as research object, various problems of trigonum stress concentration in large height mining face, intense strata behaviors, massive rib spalling of coal wall in coal mining process were solved by grouting method. Grouting scheme was analyzed in reasonable grouting area, grouting timing with vertifying from theoretical analysis, field measurement, industrial test. Based on grouting operation in trigonum, the rib macropore was filled with injecting paste material, the completeness and stability of coal-body was strengthened. The degree of rib spalling was better controlled so that achieved expected requirement of rib spalling prevention.