Truss deflection measuring instrument and using method thereof

The invention discloses a truss deflection measuring instrument and a using method thereof. The truss deflection measuring instrument includes a first base, which is installed on a support rod at theend of a truss, and a guide hole is arranged at the end of the first base; a second base, which is installed on a stand column corresponding to the end of the truss, and the second base is provided with a mounting hole; a sleeve, wherein a first end of the sleeve is installed in the mounting hole of the second base, and the first end of the sleeve is closed and a second end is provided with an opening; and an ejector rod which is installed in the sleeve, wherein a first end of the ejector rod is connected with the bottom of the sleeve through a damping device, a second end of the ejector rod extends out of the opening of the second end of the sleeve, and the second end of the ejector rod can extend into the guide hole of the first base and can slide in the guide hole. Scales are set on theperiphery of the ejector