Aiming at the requirements of ship steel plate cleaning for green shipbuilding, laser derusting with an optical fiber laser is investigated to obtain the proper process parameters to satisfy the surface quality of derusting. The relationships between groove geometry characteristics and the laser energy density are explored through the single-line laser scanning experiments. The results show that the groove depth, groove width and cross-sectional area of single-line scanning grooves are approximately linearly related to the laser energy density the under the condition that the laser energy density comes within the range of 0.5~5 J/mm². According to the requirements of ship steel plate derusting, a method to determine the process parameters for laser derusting via single line scanning groove geometry characteristics is proposed. Experiments of overlapping scanning laser derusting show that the proposed method is effective in a certain range so that laser derusting can reach cleanliness standards of ship coatings, and can obtain the specified different surface roughness. The results demonstrate that laser derusting with a pulsed fibre laser can satisfy the requirements of surface cleaning for ship steel plates.