International Safety Management Code only applicable for vessels above 500 Gross Register Tonnage (GRT) with below is exempted from the regulation. The risk of accident rate is increase when there is no standard guideline for Safety Management System onboard vessel. This monograph emphasizes on the factors affecting efficiency of vessel safety management system below 500 GRT. The significant contibutions alert that human error is the most contributing factor for ineffective management system then followed by the external factor, stability and inefficient management. This monograph highlights critical issue to have standard guideline for safety management system at the sea.