Small diameter core drilling offshore construction must rely on offshore drilling platform as the construction site. Due of the larger influence of wind, waves and other natural factors in the construction environment, the transportation, construction process, personnel safety and some other aspects are quite different with the land construction. In order to ensure the offshore core drilling safety, by the comparative analysis on the similarities and differences between dangerous sources at sea and land construction and through 3 steps of hazard identification, assessment and control, the systematic management of offshore construction risk control is carried on in platform construction and demolition, construction process, maritime traffic and personal protection and other aspects in technology and management for safe construction.