The invention relates to a near field probe range finding method and device based on laser reflection and belongs to the terahertz microscopic imaging field. The method is realized based on the near field probe range finding device. The range finding device comprises a laser, a visible light source, a visible light microscope, a photoconductive microprobe, a sample, a sample displacement bench, amotor control box, and a computer. The method comprises the following steps of S1, placing the sample on the sample displacement bench; S2, irradiating visible light on a tip of the photoconductive microprobe, and acquiring a scene near the tip in real time through the visible light microscope and a CCD detector, and transmitting to the computer for image processing and characteristic extraction,and obtaining a spacing S of the photoconductive microprobe-sample on an image scale; and S3, calculating and acquiring an actual distance d of the photoconductive microprobe-sample through a relational expression between the spacing S on the image scale and an actual spacing. The method and the device are used for accurately measuring the spacing between the photoconductive microprobe and the sample and automatically adjusting the spacing.