The invention provides an infrared image-based contact network geometrical parameter detection method and system. The method includes the following steps: arranging a thermal infrared imager on the top of an inspection van to collect an infrared image under a pantograph-catenary running state; performing gray scale-based template matching on the infrared image to obtain intersection point coordinates of a pantograph slide plate and a line of contact in the infrared image; and according to calibration of transformation from infrared image coordinates to spatial geometrical coordinates, performing coordinate transformation on the intersection point coordinates of the pantograph slide plate and the line of contact in the infrared image, thereby obtaining the height and the stagger value of the line of contact. The method is relatively high in detection precision, is not influenced by original image quality, and equipment that is used is simple in structure and relatively low in cost.