Abstract: The broken expand characteristics based on the rock mass, are the key to the calculation and design of the roof cut parameters of gob-side entry retaining technology.Taking the 12201 working face of Halagou coal mine as the engineering background, it was deduced by field measurement and theoretical analysis to study the broken expand characteristics and the control technology of gangue in the goaf.The on-site measurement results show that the roof of the goaf has undergone three processes from fall, compaction and stabilization, and the impact scope and time effect of each process could been determined; the broken expansion coefficient k after the stability of the roof in the goaf area has been accurately measured from 1.35 to 1.40, and the rationality of the 6 m cut depth was determined.Through the establishment of the mechanical model after the stability of the caving gangue, the principle of synergistic action between falling gangue and roadway support in gob-side entry retaining is revealed, and the supporting system of the single hydraulic prop, 11^#I-steel and the reinforcing steel net is put forward, and the good effect of the roadway is achieved.