Abstract: In order to reveal the anti-freezing mechanism of the air-cooled heat exchanger and then guide the energy-efficient anti-freezing operation of the indirect dry cooling power plant, the anti-freezing predicting model was developed through MATLAB platform in this paper following the energy equations and heat transfer equation of circulating water and cooling air. The water temperature distribution and critical freezing characteristics of air-cooled heat exchanger were disclosed and analyzed, under various working conditions and water/air flow patterns. The results show that, for air-cooled heat exchanger with the co-current cross flow pattern, the potential freezing position happens at the middle or outlet of the first row of the leeward side due to the reverse heating from cooling air to circulating water; for air-cooled heat exchanger with the counter-current cross flow pattern, the potential freezing position appears at the outlet of the first or second row of the windward side. Under the same working condition, the air-cooled heat exchanger with the four-row counter-current cross flow pattern has the most freezing risk, while the air-cooled heat exchanger with the six-row co-current cross flow pattern presents the best anti-freezing capability. This research could provide some theoretical supports for the energy-saving and anti-freezing operation of dry-cooling power Plant; meanwhile the established mathematical model could also be applied to the heat transfer prediction and controlling for air conditioning, refrigeration and solar power station.