Abstract: Top-coal breaking degree is closely related to caving efficiency.Top coal crushing force is the interaction from stent and roof pressure.But it is impossible to directly monitor the top-coal breaking degree on the stent.Therefore it is very difficulty to control the breaking of top coal.A fuzzy controller for top coal breaking is proposed.This is an auxiliary controller which takes support pressure p,pressure changes dp and broken time t as the control parameter of top-coal breaking.It is used to monitor and control assistedly of top-coal crushing.