A fast-assembling fixed door installation structure for a shower room includes one aluminum profile against a wall, a guide rail, a fixed door and a guide rail connecting assembly. The aluminum profile against the wall has a cavity, and is provided with a first notch along a height direction at an inner side thereof for mounting the fixed door. The guide rail connecting assembly includes a wall connector and a guide rail connector, which have an integral structure. The guide rail connector is provided on one side of the wall connector. The wall connector is installed within the cavity of the aluminum profile against the wall. The guide rail is provided with an installing groove matching with the profile of the guide rail connector.