An automatic control system and method of chillers for a data center are provided. The control system includes: a plurality of servers; a plurality of first temperature sensors, mounted at air inlets of the plurality of servers, respectively, and configured to detect temperatures at the air inlets of the plurality of servers in a real-time manner, respectively; a controller, configured to receive detected temperatures sent by the plurality of first temperature sensors, calculate an average temperature in the data center according to the detected temperatures, and generate a control instruction according to the average temperature in the data center; and an air conditioner, configured to receive the control instruction sent by the controller, and adjust a working mode of the air conditioner according to the control instruction.