This paper proposes simple and practical methods in order to overcome complex formulation and heavy computational burden of the forward kinematics of 6 앨 3-6 type parallel manipulators. Three ap-proaches for the forward kinematics are presented : one extra sensor a modified structure and novel numerical method. The proposed methods are applied to the forward kinematics of a new 6 앨 parallel manipulator with special geometry that has three internal links three external links and a moving platform of a cone shape. The proposed methods use three tetrahedrons for finding the position and orientation vector of the moving platform. The main advantages of the appraches using tetrahedrons are to abbreviate the formulation to easily find so-lutions of the forward kinematics and to be able to practically control of the manipulator in real time.