A new opening cotton device used in detecting and eliminating foreign fibers of cotton was presented in this paper. It is the first time to propose that the multi-variable nonlinear constrained optimization algorithm should be applied to obtain parameter values of the tooth profile of the opening roller and feed rollers as well as their diameter and rotating speed values. This approach was used to simultaneously consider the impact of all the performance parameters, and the important performance parameters may be weighted. As a matter of experience, the cotton fiber and foreign fibers were damaged small by the tooth profile of the opening roller and feed rollers. The foreign fibers could be easily detected and removed for they would not be torn.