Abstract: Owing to the versatile traffic big data platforms, a benefit evaluation method based on "trip mode share ratio" is developed.The method is different from traditional ITS evaluation methods which are generally based on the economic benefits of vehicle owners.Cost Savings include fares of vehicle transportation, time cost of passengers, and environmental cost (e.g.CO2 emission).Considering different income level of passengers, a comprehensive formula is proposed to calculate the time cost of different travel modes and purposes.Values of parameters are determined through a traffic big data platform.Moreover, a benefit evaluation formula of cost savings resulted from traffic mode transfers is proposed by "with and without comparison method".Take the traffic big data platform of Wuhan City as a case study, a cost-benefit analysis is carried out in terms of the influence area and selection of parameters.The method is proved to be a useful way of quantitative benefit evaluation for traffic big data platforms, and provides a guideline for future similar projects.