To alleviate the problem of soil nutrients imbalance and lower yield and quality of the upper tobacco leaves caused by tobacco continuous cropping in Pingtang County,the reasonable application time and basal/topdressing ratio of organic fertilizer were explored. Field experiments were carried out using Yunyan 87,the main cultivar as material,to investigate the effects of application time(20 and 30 days after transplanting) and basal/topdressing ratio levels(4∶1 and 3∶2) on root dry matter,root volume,enzyme activities of soil and the yield and quality of upper leaves,with 100% organic fertilizer as base fertilizer (applied when ridging) as control (CK) in 2016 and 2017.The results showed that the enzyme activity of soil was significantly increased 70 days after transplanting in the T1 treatment(20% organic fertilizer application at 20 days after transplanting)compared with control.In detail,the urease activity of soil was increased by 16.59%(2016) and 14.17%(2017) respectively,while the increase rate was 1.77% (2016) and 1.73%(2017) for phosphatase activity.Besides,the tobacco root development index of T1treatment was significantly higher than that of control.The vitality of tobacco adventitious root was increased by 11.37%(2016),9.76%(2017) respectively,the weight of root dry matter was increased by 30.02% (2016) and 19.96% (2017) respectively, and the increase rate was 32. 84% (2016) and 32.69%(2017) for root volume.The score of appearance quality and smoking quality,yield and output were maximal in T1 treatment,and there was significant difference between T1 treatment and control.In conclusion,the T1 treatment had the best effect on improving soil enzyme vitality and promoting the development of tobacco plants,and the yield and quality of upper leaves were significantly better than that of control.Thus,the T1 treatment,20% organic fertilizer application at 20 days after transplanting,contributed to improvement of the yield and quality of Yunyan 87 upper tobacco leaves in Pingtang County.