The invention discloses an aircraft engine inlet temperature measuring device which comprises a thermocouple arranged on an aircraft engine, and the output end of the thermocouple is connected with the input end of a junction box. The output end of the junction box is connected with the input end of a signal conditioning module. The output end of the signal conditioning module and the output end of a cold-end temperature compensation module are connected with the input end of a data collecting card. The output end of the data collecting card is connected with the input end of a core controller. In the signal conditioning module, two isolating sensors which can only measure positive voltage are used for replacing an isolation sensor which can measure positive voltage and negative voltage at the same time, the problem of the low measuring precision of the isolation sensor which can measure the positive voltage and the negative voltage at the same time is solved, the measuring precision is obviously improved, and the accuracy of a measuring result is ensured. The invention further discloses a measuring method of the aircraft engine inlet temperature measuring device.