The invention discloses an outdoor electromagnetic field data acquisition system, which comprises a high-temperature-resistant waterproof nonmagnetic bracket made of a nylon material, an electromagnetic field sensor arranged in the high-temperature-resistant waterproof nonmagnetic bracket, a control circuit and a solar-cell panel which is arranged at the outer top end, wherein the solar-cell panel is connected with a power supply battery pack and converts the acquired solar energy into electric energy to feed the electric energy to the power supply battery pack; an output end of the power supply battery pack is connected with the control circuit, and the control circuit stabilizes the output voltage to feed the output voltage to the electromagnetic field sensor; and an output end of the electromagnetic field sensor is connected with the control circuit, the measured data is transmitted to the control circuit, and the control circuit converts the input digital signal into an optical signal, and the optical signal is transmitted to a personal computer (PC) terminal through the optical fiber. The structure can meet the requirement on all-weather working, accords with waterproof, high-temperature-resistant and other outdoor use conditions, can effectively shield the influence of access of an external fixing device on the measured result, and finally realizes the research on on-site unmanned monitoring of power frequency electromagnetic field data.