Mounting the supporting device on the road header has totally changed the traditional temporary supporting method. The workers can avoid to work in the unsupported area, hence to improve the safety. At the same time, for this device puts a supporting force to the roof, the supporting net can also be put by it to reduce the labors. this device will extend when use and will fold after using. It is hydraulic, is very helpful to save time and improve efficiency. It is easy to operate and without interference with the work of road header.