The emergence of shared bicycle systems, such as Citi Bike, has greatly changed the pattern of urban mobility in New York City. It has not only provided a new choice for people to travel, but also greatly changed the way people live. In this paper we discuss the impact of Citi Bike on economics, society, environment and other relevant aspects. On the basis of considering people's favorable choices of travel mode, we choose car, walk, subway, bus, bike and For-Hire-Vehicle, totally four modes, to study. We select several representative indicators to evaluate the travel modes, such as the average number of users within one year, the speed, the operating cost and the impact on the environment. Then the data is standardized by the method of Deviation Standardization and we draw the data table using Excel.Then we choose the Entropy Weight Method to calculate the weight of different modes using Matlab, calculate the respective score of travel modes, and finally we get the Citywide Mobility Mode to quantitatively assess the impact of shared bikes on economics, environment and society. We reach a conclusion that without a shared bike system, the way people travel will mostly be replaced by driving. It will lead to more fuel consumption and extraneous expenses, which will increase the burden on consumers and bring pollution to the environment. During our process of modelling, the biggest challenge is to build a reasonable model to simulate the situation without a shared bicycle system, but the assumption itself is unreasonable, so this paper establishes a unified framework for all kinds of travel modes. When the shared bicycle system is not included, the proportion of it is reduced to zero, so the change of the model is observed to evaluate the impact of the shared bicycle system on the city. We hope this research helps to support the construction of transportation systems in New York and other cities around the world.