Smart agriculture is an advanced form of modern agriculture. Unmanned farm is an important way to realize smart agriculture, and intelligent agricultural machinery is the material support for unmanned farm. Took plant production of intelligent agricultural machinery in smart agriculture as an example, this paper introduced the research progress of status and key technology of four functions of intelligent agricultural machinery, including intelligent information sensing, automatic navigation, precision operation and smart management. South China Agricultural University integrated the intelligent agricultural machinery of rice production and built the unmanned rice farm. The five characteristics of unmanned rice farm are summarized as follows: 1) All production processes, including cultivation, planting, management and harvesting are unmanned; 2) Transfer between hangar and field, and operation are full-automation; 3) Avoiding obstacle and parking automatically at abnormal condition ensure the safety; 4) Real-time monitoring of all production process; 5) Unmanned intelligent decision-making and precision operation. In the production of medium rice in 2020 and early rice in 2021, the yield of rice in unmanned farm was higher than the average yield in traditional farm, which indicated that unmanned farm had great development potential. The construction of unmanned rice farm provides an important way to solve the problems of “who will farm” and “how to farm” in the future of China.