The invention discloses a method and a system for planning an optimal route and an optimal driving mode of an electric automobile. The method comprises the following steps: based on reachability analysis, performing sieving so as to obtain a practicable route set of the electric automobile under different driving modes and a corresponding charging mode set; after a user weight coefficient is obtained, calculating evaluation indexes of each practicable route under different driving modes, wherein the user weight coefficient is the coefficient preset by a user or is the coefficient which is automatically obtained according to the driving habits of the user; and based on the calculated evaluation indexes, planning the optimal route and the optimal driving mode. Through the adoption of the method disclosed by the invention, according to the demand indexes of the user, the evaluation indexes of corresponding weighting are calculated, so that the optimal practicable route, and the optimal driving mode, namely the combination of a driving mode and an air conditioner mode are obtained through sieving; and automobile characteristics of the electric automobile can be sufficiently utilized, so that the optimal route planning result and the optimal driving mode planning result are obtained, the optimizing result is good, and the method can be widely applied in the control field of the electric automobile.