The nonlinear system design problem is investigated concerning with robust stability and output tracking problems for nonlinear perturbed feedback control systems using operator-based robust right coprime factorization and isomorphism. First, a compensator is designed to factorize a nonlinear perturbed plant using isomorphism, then the right factorization of the plants can be realized. Further, by guaranteeing an output tracking property, the existence of two stable controllers is proved so that a Bezout identity for the right factorization of the plant can be satisfied. Meanwhile, the robust stability can be guaranteed by the two controllers. Therefore, the right factorization is exactly to be a robust right coprime factorization. That is, by the proposed design scheme, the robust right coprime factorization is realized and the plant output can also track to the reference input. A numerical example is given to show the effectiveness of the proposed design scheme.