The utility model relates to infrared online temperature measuring sensor and system. The infrared online temperature measuring sensor is used for detecting the temperature of a power system, and comprises an array infrared detector, a driving and signal conditioning circuit, a communication circuit, a control circuit and a power supply, wherein the array infrared detector receives infrared radiation energy of the power system, converts the infrared radiation energy into electric signals, and outputs the electric signals; the driving and signal conditioning circuit is connected to the array infrared detector, drives the array infrared detector, receives and conditions the electric signals, and outputs conditioned electric signals; the communication circuit receives external signals and transmits signals to the external; the control circuit is connected with the driving and signal conditioning circuit and the communication circuit, controls the driving and signal conditioning circuit and the communication circuit, receives and processes the conditioned electric signals, and then output processed signals to the communication circuit; and the power supply supplies power to the driving and signal conditioning circuit, the communication circuit and the control circuit.