The present invention relates to pesticides field, disclosing a seedling strengthen agent for promoting growth of plant seedling, including dexon, tachigaren, metalaxyl, paclobutrazol, uniconazole, fibrin, humic acidic ammonium, ammonium sulphate, azophoska or mixture of the three for sterilization, increasing seedling content of nucleic acid, protein and chlorophyll, changing endogenous hormones in seedling, increasing seedling resistance, improving edaphic pH value, increasing fertility and promoting growth of plant seedling in angles of sterilization, increasing fertility, etc.