Followed by modern technology development, communication plays an important role. Therefore, the demand for high-speed communication techniques snowballs. With the introduction and deployment of 5G, the need to study the fifth generation(5G) software-defined radio (SDR) has become significant in understanding transmission, flexibility, and efficiency. In 5G, one of the critical technologies that have been applied in the signal transmission process is orthogonal frequency-division multiplexing (OFDM). Instead of the traditional way of simulating signal transmission than using hardware to collect 5G data and transmit it, a software-defined radio system will be used. In this paper, an OFDM transmitter and receiver will be created and discussed through GNU Radio in an SDR system, and the corresponding constellation graph and signal wave change could be observed. The project will study what GNU Radio provided and study how 4G/5G work in the SDR system and finally demonstrate how 5G OFDM block transmits and receives the signal through the GNU radio SDR system.