One of the solutions to provide conditions for the low-income groups to use the benefits of tourism is the development of sharing accommodation and online sharing accommodation platforms. Sharing accommodation is one of the most important types of sharing economy, which is an emerging phenomenon in Iran. The essential element of the growth and sustainability of sharing accommodation is "trust". Nowadays, online sharing accommodation platforms offer mechanisms to overcome trust problems, which are known as "trust-building mechanisms". These mechanisms are a solution of mechanism design theory to solve trust problems and overcome information asymmetry between market parties. The purpose of this research is to use game theory and mechanism design theory to designing, evaluating and optimizing a new trust-building mechanisms in online sharing accommodation platforms in Iran. In this regard, after designing and evaluating a trust-building mechanism, the proposed mechanism is optimized using Pareto analytical solutions designed based on bargaining models. In this method, in order to optimize the income of participants in the mechanism designed by mechanism design theory, the optimal state of the proposed mechanism under conditions where negotiation and bargaining are possible is identified using two methods: "Nash Arbitration Scheme" and "Kalai-Smorodinsky Solution".