Abstract: A field experiment with four treatments and one check to study flowering time of flue-cured tobacco was conducted. The results showed that all treatments deferred flowering time, increased effective leaf number, yield, and output. The four treatments also increased remarkably chlorophyll content, NR and amylase activities, and N metabolism of early stage of tobacco plant, which was helpful for tobacco plant body building, and later in blooming stage, which could cause amylase activity increase slowly, thus deferred reproductive growth and early flowering.