In factory-like planting pattern of Portabella mushrooms, aiming to provide working parameters for mushroom picking robot, mushroom bed images were collected into the industrial personal computer (IPC) to measure in situ by structured light 3D camera-SR300. For complex background of plenty of hyphae in mushroom bed, the dynamic threshold was calculated adaptively by the mode of depth data of soil surface combined to at least 20mm of stipe height, and the binary image of mushroom caps were extracted from mushroom bed background. For adhesion and quasi-circular mushrooms, the centric coordinates and radius were detected roughly based on the 2-1 cyclo-Hough transform, and then the boundaries of mushrooms were tracked, denoised and interpolated to segment adhesion mushrooms and fit a single mushroom exactly. And the three-dimensional coordinates of the centric and the boundary points of a single mushroom were calculated. By the coordinate system calibration of camera, the measurement accuracy in site was verified by using a ceramic disk. The location, diameter and deviation-lean angle of a single mushroom were calculated in world coordinate system of the camera. Field test results showed that the maximum diameter error of a mushroom was 5.57mm, the maximum lean angle error of a mushroom was 6.3°. The mean run time of a video frame was 206ms, and the mean run time of a single mushroom was 44ms, which can meet the scene requirement of the mushroom picking robot.