In recent years, car-sharing has emerged and developed in different cities in China, supplementing other urban transportation modes, but also triggering fierce competition with some of them, such as taxis. In this study, we use the car-sharing orders and GPS trajectory data of a company in Beijing, China, to discuss the competitive advantages, market, and development trends of car-sharing from the perspective of travel costs. By building a travel costs comparison model, we calculate the travel costs of car-sharing and taxis under the same travel scenario, comparing their cost differences in the dimensions of travel mileage, duration, utilization efficiency, etc., and locating the cost advantage space of car-sharing. Further, we discuss the impact of different elements of travel (such as time cost, waiting time, etc.) on the cost advantage of travel by car-sharing. The results reveal that, under the current pricing conditions, the cost advantage of car-sharing is particularly obvious when the rental duration is not too long (less than 14 h), the utilization efficiency is relatively high, and the stop time is shorter than 8 h. We also find that it makes great cost advantage of using car-sharing in periods or areas of urban taxi shortages. In the cases of short travel, car-sharing have bigger cost advantage for the middle and low-income groups. In addition, the popularity of bike-sharing can also increase the cost advantage of car-sharing, which indicates that the synergy of different travel models could promote the development of car-sharing. However, when people travel long, the cost advantage of car-sharing would be minimally affected by the elements, such as people's income and the development of bike-sharing. In other words, car-sharing would keep its cost advantage in the cases of long travel, especially when its utilization efficiency is high and the travel stop time is short.