Abstract: Disclosed is a stair tread template ruler, including a main ruler body, and two side ruler bodies. Either of the side ruler bodies is provided with a sliding member that can slide in a reciprocating manner, and the main ruler body is hingedly connected to the sliding members. The two side ruler bodies are arranged at both ends of the main ruler body, and the main ruler body and the two side ruler bodies cooperate to contour a space such as a staircase. The two side ruler bodies are connected to the main ruler body, the sliding members can slide to meet various use requirements, and the main ruler body is rotatably connected to the sliding members, which facilitates adjustment of a relative angle, meets user needs, and simplifies folding and storage. The main ruler body has a multi-segment structure, and each segment is slidably connected to another.