Two revised drafts about a simple evolution trade-off function studied by Mitchell(Mitchell, 2000) were put up first. Considering the complex of the environment, or the nonlinear interaction of the environment and species, we put up two new cost functions: [formula: see text] In the first case, if the environment is adverse to species (a > 0), the region of low-stress which is more suitable for the intolerant species is very small, and at the same environment stress z, the tolerant species will pay the more cost than it will paid in the normal environment. However the tolerant species will pay more cost but low strategies in the environment of a < 0 than that it will paid in the environment of a = 0 or a > 0. In the second case, the results showed that the greater the stress of the environment is, or the more complex the environment is, the lower cost the intolerant species will pay in the region of z < 1. In order to exist or to evolve from an environment of high-stress, the organisms must possess a higher u, or a better means of mitigating of the stress of environment. Meanwhile in the region d > 1, when d decrease, the intolerant species will pays more lower cost of exploiting a habitat in the low-stress environment while the tolerant one will pays more lower cost in the high-stress environment. This means that scale d describes the selection character of the species system in the evolution process, the smaller the d(d < 1) is, the better the selection or the mitigation the system will possesses.