Abstract: The effect of Ti/N ratio on microstructure and mechanical properties of high strength low-carbon bainitic steel plate is investigated.The result shows Ti/N ratio have obvious effect on the yield of acid-soluble boron in steel and mechanical properties of that kind of steel.Boron yield of no more than 50% could be obtained when the Ti/N ratio is below 3.3,more than 75% obtained when the ratio over 3.6,and nearly 90% obtained when the ratio reaches 4.The mechanical properties of the steel are obviously improved with the increase of the Ti/N ratio.Adding enough Ti to boost Ti/N ratio is an effective and economic way to increase effective boron yield and further improve the mechanical properties.