The invention provides a low-voltage cable contact temperature on-line monitoring device which is mainly composed of a temperature data acquisition module and a temperature data collecting module. The temperature data acquisition module is mainly composed of a shell, a collecting circuit board, a temperature sensor, a collecting single chip microcomputer and a collecting infrared receiving and transmitting module. The temperature data collecting module is mainly composed of a collecting circuit board, a plastic shell, a collecting single chip microcomputer, a collecting infrared receiving and transmitting module, a time clock chip, an LED signal displaying lamp, a display screen interface, a humidity and temperature sensor and a dial switch. The temperature data acquisition module and the temperature data collecting module are in infrared communication with each other. The low-voltage cable contact temperature on-line monitoring device can achieve 24-hour real-time on-line monitoring on the low-voltage cable contact temperature, improve the accuracy degree of temperature data measurement, provide support and help for improvement of the power grid operation management level, and be compact in structure and convenient to install and implement.