Abstract: Face fall remains one of the most difficult ground control problems in single-pass thick seam longwall mining which affects the safety and production. The mechanism of face failure is analyzed using Ritz method,and the co-de- formation characteristics of the “roof-support-face” system are revealed through the 3D physical modeling study. The results show that:① The proposed face failure mechanism based on Ritz method simulates the top face fall,top and bottom face fall and entire face fall that are typically observed in the field,and the important influencing factors on face failure are determined as coal cohesion, face concentrated load, face movement and roof uniformly-distributed load. ② The physical model shows that entire face falls occur in a short time under the concentrated load and face movement. The roof displaces linearly in the vertical direction. Roof vertical displacement and face horizontal displace- ment increase at a large rate. ③ Under the protection of roof support,however,only partial face failure is observed on the face. The roof vertical displacement increases in a step function. The increase rates of the roof and face displace- ment are significantly reduced. Face maintains its stability in a relatively long time.