The disclosure provides a theodolite and vision assistance-based distributed-type POS (Position and Orientation System) alignment calibration method of flexible baselines. Two targets placed in camerafields of view in advance are respectively aimed at through a dual-theodolite system, and relationship data of the two targets and the dual-theodolite system are acquired; relationship data of the two targets are calculated through the relationship data of the targets and the dual-theodolite system; data of relationships between two cameras and the two targets are acquired through calibrating intrinsic parameters of the cameras, and calibration operation of extrinsic parameters is completed; a relationship matrix is established through the relationship data of the two targets, the intrinsic parameters of the cameras and the extrinsic parameters of the cameras, and a relative relationship between the two cameras is calibrated. The method achieves effects of non-contact measurement, simpleoperation and low cost. At the same time, a theodolite measurement system calibrates the two vision cameras without a common field of view, and achieves high-precision calibration accuracy, high efficiency and use easiness. The disclosure also provides a theodolite and vision assistance-based distributed-type POS alignment calibration device of the flexible baselines