A data center heat recovery system includes a building heat pump system providing a first liquid when an ambient temperature is lower than a first preset temperature, a heat exchanger receiving the first liquid from the building heat pump system when the ambient temperature is lower than the first preset temperature, and modular data centers. Each of the modular data centers includes an air chiller and a data center. Each of the modular data centers is coupled to the heat exchanger through a second pipeline containing a second fluid. When the ambient temperature is higher than a second preset temperature, the air chiller cools the second fluid. When the ambient temperature is lower than the first preset temperature, the heat exchanger collects heat from the second fluid, and the heat exchanger transports the collected heat to the building heat pump system through the first fluid in the first pipeline.