An expression of the distribution of load in the shrew thread of a bolt-nut connection which is subjected to not only axial forces but also to tangential forces and bending moments simultaneously is obtained in the following process. First, let an expression of the distribution of load in a screw thread be a polynomial of turning angle (angle of rotation of a point moving along the helix of the screw) as the variable whith undetermined coefficients. Next, using the above expression calculate the resultant axial force, resultant tangential forces, bending moment at the bearing surface of the bolt head, deflection and deflection angle of the bolt at a distance from the bolt heat. Then, decide the undetermined coefficients in the postulated polynomial by means of the linear programming method, so that the results from the above calculation with this polynomial approach the experimental results as far as possible.