Abstract: The paper studied the effect of top pruning and plant growth regulators on the tobacco growth and development under different potassium level by pot trail. The results showed that: plant growth regulators could increase the value of plant’s truck height, stem circumference, the maximum leaf area, section distance, root volume, fresh root weight and area of the second leaf, the BR and GA3 was more better, but there was no significantly effect on tobacco’s effective amount of leaves. There were no significantly effects of applied potassium in higher level on tobacco plant’s truck height, stem circumference, the maximum leaf area, section distance, fresh root weight and area of the second leaf, but could significantly effect on root volume increase.