A communication system for an unmanned aerial vehicle, the communication system comprising: an onboard communication apparatus configured to be mounted on an unmanned aerial vehicle and configured to operate using a preset frequency band; and a ground communication apparatus configured to communicate with the onboard communication apparatus using the preset frequency band, wherein the preset frequency band is a C-band, the ground communication apparatus is configured to communicate with a ground control apparatus through Ethernet, and the onboard communication apparatus is configured to communicate with a flight control computer mounted on the unmanned aerial vehicle through RS-232, characterized in that the ground communication apparatus includes a first baseband unit connected to the ground control apparatus, a first transmission unit connected to the first baseband unit, a first reception unit connected to the first baseband unit, a first duplexer connected to the first transmission unit and the first reception unit, and a first antenna unit connected to the first duplexer; and the onboard communication apparatus includes a second baseband unit connected to the flight control computer, a second transmission unit connected to the second baseband unit, a second reception unit connected to the second baseband unit, a second duplexer connected to the second transmission unit and the second reception unit, and a second antenna unit connected to the second duplexer, the onboard communication apparatus further includes a divider configured to divide frequencies or times and interposed between and connected to the second duplexer and the second antenna unit, and the second antenna unit includes a first antenna and a second antenna configured to be mounted on different positions, the divided frequencies or times are transmitted through the first antenna and the second antenna, the first antenna is configured to be mounted on a top of the unmanned aerial vehicle, and the second antenna is configured to be mounted on a bottom of the unmanned aerial vehicle. an onboard communication apparatus configured to be mounted on an unmanned aerial vehicle and configured to operate using a preset frequency band; and a ground communication apparatus configured to communicate with the onboard communication apparatus using the preset frequency band, wherein the preset frequency band is a C-band, the ground communication apparatus is configured to communicate with a ground control apparatus through Ethernet, and the onboard communication apparatus is configured to communicate with a flight control computer mounted on the unmanned aerial vehicle through RS-232, characterized in that the ground communication apparatus includes a first baseband unit connected to the ground control apparatus, a first transmission unit connected to the first baseband unit, a first reception unit connected to the first baseband unit, a first duplexer connected to the first transmission unit and the first reception unit, and a first antenna unit connected to the first duplexer; and the onboard communication apparatus includes a second baseband unit connected to the flight control computer, a second transmission unit connected to the second baseband unit, a second reception unit connected to the second baseband unit, a second duplexer connected to the second transmission unit and the second reception unit, and a second antenna unit connected to the second duplexer, the onboard communication apparatus further includes a divider configured to divide frequencies or times and interposed between and connected to the second duplexer and the second antenna unit, and the second antenna unit includes a first antenna and a second antenna configured to be mounted on different positions, the divided frequencies or times are transmitted through the first antenna and the second antenna, the first antenna is configured to be mounted on a top of the unmanned aerial vehicle, and the second antenna is configured to be mounted on a bottom of the unmanned aerial vehicle.