Abstract: Electric heating is one of the ways to in-situ retorting oil shale, and electric heater is the key heating component. Through simulating temperature distribution of electric heater by PDE tool in MATLAB, this paper discusses the effect of heat conductivity coefficient of the heater, heat source density, density, specific heat capacity, heater size, etc. on heater effectiveness and uses these parameters as the basis for design optimization of electric heaters. The research findings show that the materials with low density is helpful in improving heating efficiency of the heater; the heat conductivity coefficient poses small effect on the temperature; the higher the specific heat capacity is, the lower the overall temperature of the heater is; with the increase of heat source density, the temperature of the heater is increased remarkably. Orthogonal experiment shows that heat source density, density and specific heat capacity have great effect on heater temperature distribution, while heat conductivity coefficient has little effect; with the increase of heater radius, the temperature increases accordingly. The heater of design optimization takes the shape of U-tube and vacuum heating tube with axial symmetry, and the materials of heating components are copper and stainless steel, etc. Downhole in-situ electric heating can not only be used for development of oil shale, but be used as a technique for developing heavy oil.