The invention discloses a bar adjusting positioning and clamping device for a mechanical arm. The bar adjusting positioning and clamping device for the mechanical arm comprises a pedestal and a bar transferring positioning and clamping mechanism arranged at the front end of the pedestal. The bar transferring positioning and clamping mechanism comprises a lower pedestal body connected with the front end of the pedestal, a bar transferring mechanism arranged on the lower pedestal body and an upper clamping mechanism arranged on the lower pedestal body and matched with the lower pedestal body toclamp a bar. The bar transferring mechanism comprises a first driving mechanism, a driving gear set, a driven gear set, a rotation coder, a clamping jaw and a clamping jaw detecting mechanism. The first driving mechanism is arranged on the pedestal, the driving gear set is arranged at the bar positioning end of the lower pedestal body and connected with an output shaft of the first driving mechanism, the driven gear set is arranged at the input end of the lower pedestal body and is in transmission connection with the driving gear set through a transmission belt, the rotation coder is arrangedon the lower pedestal body and used for detecting the rotating angle of a driven shaft of the driven gear set, the clamping jaw is arranged on the transmission belt, and the clamping jaw detecting mechanism is used for detecting whether the clamping jaw returns to an initial/reset position or not.