Abstract: Automatic spraying apparatus for pipeline coating is developed aiming at the characteristics of a on-line pipeline in coating rehabilitation, small excavation area and limited working space domestically. Analysis is made on working principle of the apparatus, and its mechanical structural design and principle of control system are set forth meanwhile. Field test is carried out in Northern Pipeline for its application. Results show that the apparatus can operate surface spray over an in-service pipeline automatically and work steadily and reliably, with good atomizing effect and even spraying thickness. The apparatus can make automatic rectification and control operation automatically.