Inner diameter control ruler for drainage well

The utility model belongs to the technical field of construction, and particularly relates to a drainage well inner diameter control ruler which comprises a measuring rod, at least three inclined supporting rods are hinged to the lower end of the measuring rod, a sleeve is arranged in the middle of the measuring rod in a sleeved mode, and scales are arranged from the middle to the upper end of the measuring rod. The middle of each inclined supporting rod is hinged to one end of an adjusting rod, the other end of each adjusting rod is hinged to the middle of the sleeve, and when the sleeve slides on the measuring rod, the adjusting rods can drive the included angle between the inclined supporting rods to change. When the diameter of a well mouth is measured, the adjusting rod is directly expanded according to the diameter of a closing opening, the scale reading corresponding to the sleeve is the expanding radius, the measurement is very convenient and efficient, and the device can adapt to different inner diam