The invention discloses a measuring method of landslide or rock mass deformation in construction excavation, and relates to the field of geological hazard investigation and design and prevention and control of slope engineering. The measuring method of the landslide or rock mass deformation in the construction excavation comprises the following steps that step 1, a first hole is drilled at a landslide body or the upper part rock mass of an outward inclined structural plane, and a second hole is drilled at a sliding bed or the lower part rock mass of the outward inclined structural plane; step2, a measuring needle is inserted into the first hole, and a scale ruler is inserted into the second hole; step 3, the topographic slope of an open-air slope at a shear exit of landslide or rock massdeformation is a, an inclination angle of a sliding zone or the outward inclined structural plane is b, the height of the measuring needle and the sliding zone or the bottom of the outward inclined structural plane is h1, and the height between the measuring needle and the scale ruler is h2; and step 4, the horizontal displacement of a pointer on a dial is recorded every day, and a time-horizontaldisplacement graph is manufactured. The measuring method of the landslide or rock mass deformation in construction excavation realizes that the equipment preparation is convenient, the installation is relative simple, and the method is feasible and practical.