To design a force/tactile feedback device with compact construct and a larger workspace, the kinematics analysis and working space algorithm were researched based on the Delta mechanism. Based on the improved Delta mechanism, a chain offset angle alpha was introduced. Positive and inverse kinematics were established by the vector method and their correctness were verified by taking a deduced equation as an example. According to the inverse kinematics formula, the envelope body equation of single-open-chain subspace was deduced and the geometric shape of the subspace was drawn under three situations while the length of drive rod is more than or equals to or less than that of oscillating rod. Then the influence of alpha on the whole workspace and mechanism size was deeply discussed. The relations between the offset angle and the volume of the maximum inscribed sphere, the offset angle and the whole mechanism size were derived using the numerical method. Moreover, the cross section view of the space was plotted by MATLAB. Finally, the maximum inscribed sphere was taken as the design space,and a design example was given by using the Jacobin matrix condition number. The results after verifying show that the designed mechanism meets requirements of optimized design Delta mechanisms.