  The PandaX-III experiment uses high pressure gaseous time projection chamber
to search for the neutrinoless double beta decay of $^{136}$Xe. A modular slow
control system~(SCS) has been designed to monitor all the critical parameters
of the experiment. It ensures the proper operation of the experiment as well as
to provide necessary information for data corrections. The main subsystems of
the experiment will be constantly monitored by the data collection module of
the SCS, which collects data from sensors and sends them to the centralized
database. When an alarm message is generated by the anomaly detection module,
it will be sent to an alert website and related on-call experts immediately. A
demonstrator of the SCS has been built for the PandaX-III prototype detector.
The long-term test of it provided valuable experience for the final design of
the SCS for PandaX-III.
