Abstract: Fast and accurate faults diagnosis can dramatically improve the efficiency of ship water fire-fighting.A method combined the graph theory with empirical formula was presented.It chose the empirical formula results based on the repair time of the faults as the weight for the arcs in the diagnosis path,which adopted＂reserve-track＂ to calculate the shortcut from damaged status to the specific repairable equipment and ascertained th he fault diagnosis order.The results show that the diagnosis order, governing almost all of the fault-repair principles which influence the water fire extinguishing system, is practical and accorded with the practical applications.