Abstract: The integration system of underground mining and beneficiation is an effective method for developing deep ore bodies with high efficiency，low-cost，low carbon, and it can  achieved sustainable development.Besides，this system is suitable for densely populated areas，severe cold district and the area where need strict environmental requirements.In this system，the question of the balance between mining and filling should be considered firstly，that is，all of the tailing should be used for bashing.Therefore，the critical grade to achieve a balance between mining and filling is a significant indicator to evaluate whether the system is perfect.This paper studied the affecting factors of the critical grade，and derived the general formula of the critical grade.The analysis software of the critical grade to achieve a balance between mining and filling is developed，which can work out the critical grade according to different geological，dressing and filling ratio conditions.It can also analyze the variations of the critical grade at different conditions，providing the scientific basis for the application of the integration system of underground mining and beneficiation.

Key words: Integration system of underground mining and beneficiation, Balance between mining and filling, Critical grade, Affecting factors