A mathematical model has been established for the research on scissor elevator for ship passenger stairs. The kinematical and kinetic simulation analyses were carded out with MATLAB/Simulink. The relative kinetic relation between hydraulic cylinder and other parts, as well as its rules of change has been found. A 3-D model of ship scissor elevator was established with Pro/E. The design of the mechanism was optimized in Pro/MECHANICA based on the findings from simulation analysis. Practice has proved that the design is scientific and reasonable and could serve as the theoretical guidance and reference for the design of scissor mechanism of other uses.