The invention discloses a detection system and a detection method for detecting the perpendicularity of a pile hole. The detection system comprises a display device, a fixing device and a distance measuring device, wherein the fixing device is used for fixing the display device above the pile hole, the distance measuring device is electrically connected with the display device and is positioned just below the display device when in use, and a plurality of distance measuring transmitting probes which are used for measuring the horizontal distance between the distance measuring device and the hole wall of the pile hole in different directions are arranged on the outer side surface of the distance measuring device. By utilizing the detection system and the detection method to detect the perpendicularity of the pile hole, the perpendicularity of the pile hole and the diameter of the pile hole can be preferably controlled, the hole forming quality of a manual hole digging pile is guaranteed, potential safety hazards of construction personnel for going up and down the pile hole are eliminated, the construction time and manpower and material inputs are saved, and the measuring time is saved.