Downhole pressure and temperature monitoring of oil production wells is one of the effective means to ensure normal and efficient development of oil and gas wells. Aiming at the problems of the conventional ways such as using production logging or under-wire manometers, the method is proposed which transmit downhole information using wireless low-frequency electromagnetic wave. Firstly, the equivalent theoretical model of electromagnetic wave transmission in oil production wells is established based on the equivalent transmission line theory, considering on comprehensive factors such as tubing, casing and annulus medium, which heavily influence the performance of electromagnetic wave transmission. Secondly, the law of electromagnetic wave transmission in casing wells is analyzed in detail when the downhole transmitter is located in the casing; Thirdly, the electromagnetic wave transmission model based on the COMSOL Multiphysics platform is studied. The simulation results show that (1) In oil production wells, the amplitude of the signal received on the ground with casing is higher than that of bare wells. The conduction current is transmitted partly in the formation and partly in the coupling channel formed by the tubing and casing inside the casing. (2) Conductivity is another important factor affecting transmission performance. The higher the electrical conductivity of the casing, the stronger the signal received on the ground. (3)The proposed electromagnetic wave transmission model can be used to explore and study the influence of casing on electromagnetic wave transmission, and also provide theoretical basis for the promotion and application of electromagnetic wave wireless transmission technology in oil and gas wells.