The utility model relates to a colliery upper corner gas sealing wall building block and forming die thereof to solve the problem that colliery upper corner gas sealing wall shutoff effect is not good, the construction is inconvenient among the prior art. Colliery upper corner gas sealing wall building block includes that center support personally experiences sth. Part of the body, and still including surrounding the whole outlying elasticity overburden at the center support body, the surface of elasticity overburden is laminated in order to form sealed fitting surface with the side that corresponds of other building blocks for being used for. Forming die includes forming box, and forming box has the center support body of confession building block and packs into and respectively upwards forming spaced die cavity, the last filling opening that supplies to be used for forming the expanded material injection of elasticity overburden that still is equipped with of forming box with the center support body. Above -mentioned building block can form the good effect that blocks to gas, compares with adopting the braided bag that is equipped with coal or soil among the prior art, and the shutoff is effectual to adopt the center support physical stamina enough to obtain higher support intensity, improve the supporting performance, reduce the potential safety hazard.