Abstract: In order to investigate the influence of hydrogen content in aluminum melt on the quality of dip aluminum coating of Q235 steel plate,hydrogen analyzer and SEM were used to study the relationship between inclusions and hydrogen content in aluminum melt.The formation reason of the defects in aluminum coating and the role of hydrogen were analyzed.The results show that under 80% humidity condition,the hydrogen content increased dramatically in the melt after heating for a long time.The inclusion could increase the hydrogen content obviously,with the increase of hydrogen content in the melt,the quality of the hot dip alumiumm coating became worse,gas bubles and plating leakage appeared.