Urban issues become more complicated and complex as the city grows, requiring better management to create a comfortable, safe, sustainable, and sustainable city atmosphere. Implementing the concept of smart city is one solution that can be used to perform better management of the city. Many major cities have started the development of smart city, including Makassar. The development of infrastructure to support the implementation of smart city in Makassar has been going on at this time, such as the addition of Wifi Corner in several points of Makassar. The technology that can be applied in supporting smart city infrastructure is wireless sensor network. This research resulted a design of wireless sensor network by utilizing the wireless public infrastructure that has been available in the city of Makassar today. The design is simulated by involving 2 sensor nodes, 1 gateway sensor node, and public wireless network. Each sensor node obtains the environment values, such as temperature, humidity, CO2, and water level. The environment values are sent to the server by the sink node. The process of sending sensor data based on requests from the server automatically and periodically to avoid network congestion on the wireless public network. All data will be displayed to be a decision support for the Government of Makassar City in anticipating the problems of the city, such as traffic congestion and floods. The design of wireless sensor network is expected to become the main infrastructure as a supporting component of smart city in Makassar using public infrastructure. The obtained data from WSN are expected to be processed using artificial intelligence's algorithms to provide the useful information to users using the public infrastructure.