Abstract: As for the repeated mining working face of second mining resulted from the old method of "digging top coal and leaving bottom coal", the roof of which is random with goaf and pillars mixed, the defining methods for setting load and working resistance used in common working faces are not suitable. In consideration that the setting load in goaf is too high to break the top coal, as well as the concentrated stress under the pillars and the collapse of old roof, support and surrounding relationship was analyzed by using corresponding mechanical models.The support setting load and working resistance of repeated mining face under goaf and pillar two different state roof were calculated. The proposed quantitative calculation formula was also verified in the field of engineering practice.