Considering an inclined rough retaining wall under the general conditions such as curvilinear fill, cohesive soil and uneven surface load, the functional extreme-value isoperimetric model about passive earth pressure is deduced based on the force equilibrium equations of the sliding mass. Then, the model can be transferred into a functional extreme-value problem with two undetermined functions by introducing Lagrange undetermined multiplier. According to Euler equations, Logarithmic spiral slip surface and normal stress distribution along the slip surface are obtained. Combined with the boundary conditions and transversality conditions, the conditional functional extremum problem of passive earth pressure involves searching the minimum of unconstrained optimizations of function with two unknown Lagrange multiplier. Results show that the passive earth pressure resultant force is minimal when the point of resultant force is on the lower bound and it increase nonlinearly as the point of resultant force moved up to the upper bound for general soil. Accordingly, the slip face evolves from logarithmic spiral face to plan. Although the magnitude of passive earth pressure reaches maximal that is the same with result calculated from Coulomb's theory, the application point of earth pressure is not at 1/3 height of the retaining wall. In addition, curvilinear fill and uneven surface load have significant effect on both the magnitude and location of application point of passive earth pressure.