With the continuous development of photoconductive microwave technology towards high-frequency, high-power, long-life, and high-efficiency directions, lateral photoconductive devices have the potential to achieve high photoelectric gain and high main frequency response due to intrinsic light triggering and low parasitic capacitance. We investigated the photocurrent response of intrinsic light back-illuminated lateral silicon carbide (SiC) photoconductive switches. Based on semiconductor numerical simulation, the output photocurrent of the device under intrinsic light triggering with different substrate thicknesses and different light powers was compared for front and back illumination. The internal current and electric field distribution of the device were analyzed and compared. Finally, experimental tests were conducted on the front and back triggering of a 50 μm lateral SiC photoconductive switch. The experimental results show that under a 40 kW peak light power, the on-resistance of the back-triggered device is reduced by 40% compared to the front-triggered device, confirming the high photoelectric conversion efficiency of the back-illuminated device, and the internal electric field and current of the back-triggered device are more uniform, which is more conducive to improving the device’s high-power capacity. The results provide simulation and experimental references for the intrinsic triggering of planar photoconductive switches.