12 Novel precision mechanical design for ellipsometer is developed. To develop several properties of precision ellipsometer, the kinematic coupling is used at specimen stage and connecting parts between mainframe and analyzer unit, and connecting part between mainframe and polarizer unit. Homogeneous transformation matrix describes all ellipsometer components and the process of light transmitting through ellipsometer components. Geometrical error analysis is performed in order to minimize the incident alignment errors. As a result of that, the rotational error of light source is most dominant on the error of detected signal. The error bound is +/- 0.08 degree(s) for light source. The translational errors of ellipsometer components don't affect the detected signals. We manufactured a precision ellipsometer using the above- analyzed results and kinematic coupling principle. The manufactured ellipsometer has many good properties, such as precise alignment of incident angle and low manufacturing cost and so forth.