The invention discloses a fixing device used for instrument mounting and facilitating angle adjustment. The fixing device comprises a bottom plate, a first mounting groove and second mounting grooves.First through holes are formed in the bottom plate, and connecting plates are arranged on the outer side of the bottom plate; the first mounting groove is formed inside the bottom plate, a connectingrod is mounted inside the first mounting groove, a second through hole is formed inside the connecting rod, and a pressure gauge is mounted inside the second through hole; and the second mounting grooves are formed in the top end of the connecting rod, connecting springs are mounted inside the second mounting grooves and fixedly connected with limiting blocks, the limiting blocks are mutually connected with limiting grooves, and the limiting grooves are formed in the upper surface of the bottom plate. According to the fixing device used for instrument mounting and facilitating angle adjustment, mounting work is conducted through the first through holes and the connecting plates on the bottom plate, the stabilizing effect of the mounted fixing device is improved, and the fixing device is prevented from shaking.