Generally, natural scientific problems are so complicated that one has to establish some effective perturbation or nonperturbation theories with respect to some associated ideal models. In this Letter, a new theory that combines perturbation and nonperturbation is constructed. An artificial nonlinear homotopy parameter plays the role of a perturbation parameter, while other artificial nonlinear parameters, of which the original problems are independent, introduced in the nonlinear homotopy models are nonperturbatively determined by means of a principle minimal sensitivity. The method is demonstrated through several quantum anharmonic oscillators and a non-hermitian parity-time symmetric Hamiltonian system. In fact, the framework of the theory is rather general that can be applied to a broad range of natural phenomena. Possible applications to condensed matter physics, matter wave systems, and nonlinear optics are briefly discussed.PACS numbers: 02.90.+p, 42.65.Tg In general, natural scientific problems cannot be exactly described by some analytical expressions. What scientists usually do is just first to establish some ideal models, and then to consider additional effects by use of some perturbation and nonperturbation theories.Perturbation theories (PTs) [1, 2] already have quite a long and interesting history in physics. They have been used to explore physical systems that can not be solved exactly but with a small parameter. Though great challenges are coming from the blooming numerical calculation methods, PTs are still showing their great power in solving various problems. For instance, perturbation theories have been used to study the spectrum of non-hermitian parity-time (PT ) symmetric Hamiltonian [3], the structure of trapped Bose-Einstein condensates (BECs) with long-range anisotropic dipolar interactions [4], and the interacting fermions in two-dimensions [5]. Besides, the fundamental ideas of PTs have been utilized to study some models in quantum computation theory (QCT). Techniques based on PTs have also been applied to engineer interesting Hamiltonians, whereby the outstanding perturbation theory gadgets (PTGs) technique was developed [6,7]. A short but incisive review of the history of PT and its new development in quantum manybody theory, quantum computation and quantum complexity theory has been given recently by M. M. Wolf [8].On the other hand, nonperturbation theories (NPTs) have been established to solve real scientific problems with the lack of a small parameter that acts as a perturbation parameter. In this case, some parameters will be artificially introduced as some formal perturbation parameters and/or nonperturbation parameters. Usually, one of these artificial perturbation parameters have to be set finite, say, the unit one, while others will be determined in some nonperturbative ways such as some types of optimized approaches.Considering the fact that physical quantities should be independent of any particular perturbation and/or nonperturbation method used to calculate them, Ste...