Knotter is the key part of square baler, and the design difficulty is the angle measurement between 5 shaft hole, that is because five shaft holes is non-paralleling, also non-crossing, the conventional methods is difficult to be used to measure the space angles. An improved parameterization definition is used to construct geometric distance functions of cylinder; secondly the nonlinear least squares solution is used to fit the cylinder in Imageware12. The fitted cylinders are introduced into UGNX3 to express the space angles in three-face projection way.