To improve photovoltaic hosting capacity of distribution networks, this paper proposes a novel optimal static var compensator planning model which is formulated as a two-stage stochastic programming problem. Specifically, the first stage of our model determines the static var compensator planning decisions and the corresponding photovoltaic hosting capacity. In the second stage, the feasibility of the first stage results is evaluated under different uncertainty scenarios of load demand and photovoltaic output to ensure no constraint violations, especially no voltage constraint violations. In addition, we simultaneously consider the minimization of static var compensator planning cost and the maximization of photovoltaic hosting capacity by formulating a multi objective function. To improve the computational efficiency, a solution method based on Benders decomposition is developed by decomposing the two-stage problem into a master problem and multiple subproblems. The effectiveness of the proposed model and solution method is validated on modified IEEE 37-node and 123-node distribution systems. Last, our results show that the proposed model can significantly improve the photovoltaic hosting capacity. The case studies also demonstrate that the PV hosting capacity becomes insensitive to the additional SVC planning cost when the total cost exceeds about $175,000.