The door operator in metallurgical equipment is a spatial 6-bar linkage mechanism. The numerical model of motion and force of the mechanism was developed and the numerical solution was applied. A computer simulation was implemented. There is a high level of consistency between the solution and simulation. The torques required on driving crank have been studied. The influences of the self-lock conditions on the crank length and con-rod length have been explored. The effects of the length of crank and con-rode on the needed maximal torques of the crank have been studied, too. And the kinematics analysis attributes the lightening design of the slider structure on the basis of considering the slider's rigidness and intensity.