Portable tree diameter at breast height measuring instrument

The utility model discloses a portable tree diameter at breast height measuring instrument, which comprises a support rod; the lower end of the measuring mechanism is connected with the upper end of the supporting rod, and the measuring mechanism comprises two V-shaped measuring rods with upward openings; and a plurality of measuring devices which are uniformly distributed along the length direction of the measuring mechanism. Each measuring device comprises two measuring blocks, and the two measuring blocks are symmetrically arranged left and right and are respectively arranged on the inner side surface of one measuring rod; a groove is formed in the position, corresponding to the measuring block, of the inner side face of each measuring rod, a through hole is formed in the bottom face of each groove, a connecting rod is movably arranged in each through hole in a sleeved mode, the inner end of each connecting rod is connected with the bottom face of the corresponding measuring block, and the outer end of eac