The invention relates to a roadway spatial deformation measuring device and a measuring method based on the device, which belong to the technical field of rock mass mechanical parameter measurement, and aim to overcome the defect in the prior art that the accuracy rate of roadway spatial deformation measurement is low. The roadway spatial deformation measuring device comprises a base point fixing member, a perforated steel ruler and a host, wherein the perforated steel ruler and the host are of a detachable structure, the host comprises a hook, an adjusting nut, a data processing and display device, a three-dimensional compass, calipers, a rule hole pin and a ruler connecting frame, the base point fixing member comprises a first base point fixing member and a second base point fixing member, the perforated steel ruler is connected with the first base point fixing member through the hook, the perforated steel ruler is fixed to the ruler connecting frame via the calipers by inserting the ruler hole pin into a circular hole of the perforated steel ruler, the ruler connecting frame is connected with the three-dimensional compass, the three-dimensional compass is further connected with the data processing and display device, the data processing and display device comprises a control unit and a display unit, the data processing and display device is connected with the hook through the adjusting nut, and the hook is connected with the second base point fixing member. The roadway spatial deformation measuring device and the measuring method based on the device are suitable for measuring rock mass mechanical parameters.