To solve the problems of current methods in processing the uncertain nonlinear system with input constraints, such as complicated computation and the large errors, we proposed a step-by-step controller-designing method with finite-time stability. In the process of the control design, an unsaturated finite-time controller of the system was designed by adding a power integrator. Then, when the output of the controller exceeded the bounded upper-limit output, the functional knowledge was used to prove that the system was finite-time stable at that time and that the segment point was existed, and the selection rules of the corresponding parameters were given. As a result, the segment handling of the input-constraint problem was realized. Simulation results proved the effectiveness of the proposed method.