This paper suggested the mathod to estimate the life of steel deck plate in bridge and applied the traffic of passing vehicles to the result of fatigue test of closed trough rib and investigated the life of crack initiation and fracture life. The life of steel deck plate is proved very important to investigate the axial distance, the numbers of wheel and the position of wheel load on bridge. In designing bridge by steel deck plate, the misalignment of trough rib is desirable to allow up to 2.0mm. As shown in the data, the data is obtained from the vehicles more than 10.0t in the axial loads of passing vehicle. considering the fatigue strength in bridges, when the axial loads of the vehicles which are more than 14.4t pass through the deck plate, the fatigue life of trough rib becomes shorter. However, when trough rib designed by high tensile strenth steel, the fatigue life becomes longer. This study shows that when the size and number of axial load more than 10.0t only acted on deck plate, the fatigue life of test specimen was estimated. Accordingly, considering axial load less than 10.0t, the enduring life of test speciman will be rather shorter than the estimated life by ${Delta}{sigma}=6.6kg/mm^2$.