This paper presents a new formulation to simplify the three resulting constraint equ ations of the direct kinematics of the 3-6 (Stewart-Gough) platform. The conventional direct kinematics of the 3-6 Platform has been formulated through complicated steps with trigonometric functions in three angle variables and thus results in the omputatio nal burden. In order to reduce the formulat ion complexity, we replace an angle variabl e into a length one and express three conne cting joints on the moving platform in the same frame. The proposed formulation yields considerable abbreviation of the number of the caculation ters involved in the direct kine-matics. It is verified through a seri es of simulation results.