The invention discloses a method for 
heating oil shale underground in situ. According to the method, 
shale oil and 
fuel gas can be obtained from an underground 
oil shale seam in situ, and the 
fuel gas can also be obtained from an underground 
coal seam in situ. Wells are drilled downwardly from the ground surface, and the drilling depth of each well reaches the inside of an operation region of an underground 
oil shale ore 
bed. At least two wells are drilled, and electrodes are placed in the wells. Firstly, high-
voltage electricity which is sufficient to cause 
partial discharge of the 
oil shale ore 
bed is conducted into the electrodes, and then a 
plasma channel is formed in the oil shale ore 
bed and can be subjected to breakdown by the high-
voltage electricity; after the resistance of each of two 
electrode regions is lowered, the two electrodes are used for conducting currents into the 
plasma channel in the oil shale ore bed; the oil shale ore bed is heated under the resistance heating function of the 
plasma channel; and released heat is used for realizing thermal 
cracking and gasification of fixed organic carbon in the oil shale ore bed. Through the method for heating the oil shale underground in situ, the heating speed of an underground ore bed can be increased, 
hydraulic fracturing does not need to be carried out on a rock stratum, and the use of poisonous 
conductive materials is avoided at the same time.