A method for measuring objects in digestive tract based on an imaging system is provided. The imaging system enters a calibration stage, and obtains a calibration image. A measurement stage enters, and the imaging system places in the digestive tract to capture at least one detection image. The depth distance zi from each pixel in the detection image to the imaging system is calculated, and it records as a depth image z(x, y). The scale r of each pixel in the detection image is calculated according to the depth image z(x, y). The actual two-dimensional coordinates Si′ of each pixel point in the detection image are calculated by the scale r, and the actual three-dimensional coordinates (Si′, z(x, y)) of each pixel are obtained. The distance between any two pixels in the detection image or the area within any range is calculated.