Extremely low frequency electromagnetic waves have been widely used in marine resource exploration，marine pollution source real-time monitoring，natural disaster prediction，marine assisted navigation， national defense monitoring and so on. It is of great significance to study on them. In this paper，experiments on the characteristics of extremely low frequency（ELF）electric field are carried out on land. The propagation attenuation law of electric field intensity generated by horizontal electric dipole（HED）is verified by theoretical analysis and experiments. The test results show that the signal response intensity decays rapidly when the transmitting-receiving distance is 0~10 km，and the signal intensity decays slowly when the distance is 10~25.4 km. The signal response tends to be flat when the distance exceeds 25.4 km. The wave velocity measurement experiment is carried out to prove the existence of underground channel when electromagnetic wave propagates. The test results show that the velocity of 1 Hz electromagnetic wave on land is about 55 km/s，corresponding to the conductivity σ= 0.0033 S/m， which proves the existence of underground channel.
