The reserve sharing amongst the interconnected power systems will facilitate the improvements on their anti‐disturbance capability and operating economy. Based on the design of reserve sharing mechanism across different areas, a multi‐area generation‐reserve sharing model is constructed. The stochastic fluctuation of load and wind power will cause the power grid to be in an unpredictable random state when the reserve is needed, and the transmission capacity constraint of the power grid may restrict the effective deployment of the reserve. To address these issues, a max‐min bi‐level optimization model is proposed to check the reserve availability. The joint generation and reserve optimization sub‐model, together with the reserve check sub‐model, constitutes the two‐stage robust optimization model in this paper. The column‐and‐constraint generation (C&CG), algorithm is adopted to solve the proposed model. The modified IEEE 118‐node test case is used to verify the proposed model and algorithm. The test results indicate that the proposed method can realize the multi‐area generation‐reserve joint optimization under the condition of guaranteeing the reserve availability, and it possesses the advantage of high efficiency in dealing with stochastic scenarios.