According to the principle of the fluid flow in porous media of oil reservoir, by taking the quadratic-gradient term, effective well bore radius and well bore storage into consideration, the nonlinear fluid flow mathematical model for dual-porosity media reservoir is established in the case of the variable flow-rate. By using the Laplace transform and reasonable approximate process, the similar structure (which is only determined by the inner boundary conditions) of dimensionless reservoir pressure and bottom hole flowing pressure and similar kernel functions (which are only in connection with basic solution set of the definite solution problem and outer boundary conditions and furthermore different outer boundary conditions correspond to different similar kernel functions, having nothing common with inner boundary conditions) are obtained in Laplace space. This study not only reveals essential characteristic of fluid flow in dual-porosity media, but also provides a new analytical theory for studying in depth the nonlinear fluid flow law of this kind of reservoir. Furthermore, it greatly facilitates programing relevant well test analysis software as well, which is potentially useful in more extensive applications.