The invention provides a deep hole drill cutter welding strength detection device and relates to a strength detection device. The problems are solved that there is no device for detecting a strength after welding of a blade on a deep hole drill and a guiding block, and thus critical values of the blade and the guiding block for stress damage after welding with the cutter in the prior art. A deep hole drill is fixedly connected on a clamp vertically. A torsional force measuring instrument comprises a transfer rod fixedly connected with a data display screen and a torsion head fixedly connected with one end of the transfer rod. A piston rod of a first hydraulic cylinder in a first hydraulic force application mechanism is fixedly connected with the other end of the transfer rod. The lower end of the torsion head matches the outer contours of the blade and the guiding block on the deep hole drill in shape. A second hydraulic cylinder in a second hydraulic force application mechanism is arranged above the torsion head vertically. A contact head of a pressure dynamometer is arranged between the second hydraulic cylinder and the torsion head. The provided detection device is used for strength detection of the blade and the guiding block after welding.