The invention relates to an internet-of-things-based mobile spraying vehicle group control system and method. The system comprises a plurality of spraying vehicles, a spraying state acquisition module, and single-chip microcomputers. The single-chip microcomputers are installed on all spraying vehicle; the spraying state acquisition module is connected with an execution module by the single-chip microcomputers; the execution module is connected with solenoid valves arranged on spraying vehicle high-pressure spayers; the single-chip microcomputers carry out interaction with a remote terminal and are connected with a power supply module. The spraying state acquisition module is used for collecting surface temperature and humidity information of a precast beam; and the single-chip microcomputers are used for carrying out calculation based on the surface temperature and humidity information of the precast beam to obtain interval time for opening the solenoid valves and spraying time and opening or closing the solenoid valves by using the execution module. According to the invention, surface temperature and humidity information of a precast beam can be collected in real time, so that the spraying water yield can be controlled precisely, the spraying effect is guaranteed, and the human negligence can be avoided. Besides, with the spraying vehicles, moving in a beam field is realized and multi-times mounting and dismounting of spraying maintenance equipment can be prevented.