Machine tools with parallel structures are the subject that usually discuss in many researches. Users are still largely unaware of the advantages offered by these new machine structures. This paper presents the development of a mathematical model describing the kinematics problem and analysis workspace of five-axis milling machine (FMM) based on six-degree-of-freedom (6DOF) structure. In addition, reachable workspace features and parameters optimization as criterion of the maximum of working volume for PM are considered.