[Objective] The effect of particle sizes of super absorbent ploymer on soil moisture and flue-cured tobacco(Nicotiana tabacum) growth was studied in order to provide scientific support for improving soil moisture and flue-cured tobacco growth in Qinba Mountain area.[Methods] The experiment took no super absorbent polymer application as control, powder (particle size < 0.18 mm), fine granularity (particle size 0.18~2.25 mm) and granularity(particle size 2.25~3.25 mm) of potassium polyacrylate super absorbent ploymer as the research materials in yellow brown soil of Qinba Mountain area, the effects of different particle sizes of potassium polyacrylate super absorbent ploymer on soil moisture, soil bulk density and flue-cured tobacco growth, flue-cured tobacco quality and flue-cured tobacco economic properties were investigated.[Results] The soil moisture of 0-40 cm soil layer were increased and the soil bulk density of 0-40 cm soil layer were reduced by potassium polyacrylate super absorbent ploymer with different particle sizes in different growing stages of flue-cured tobacco, but there was no significant effect on soil moisture under 40 cm soil layer. Among different particle sizes of potassium polyacrylate super absorbent ploymer, fine granularity potassium polyacrylate super absorbent ploymer had great influence on soil moisture and soil bulk density. Potassium polyacrylate super absorbent ploymer with different particle sizes could promote root growth, stem growth and leaf growth of flue-cured tobacco, increase tobacco yield and tobacco output value, and reduce the proportion of inferior tobacco, and fine granularity potassium polyacrylate super absorbent ploymer had a great effect on the largest leaf growth, root growth, tobacco yield and tobacco output value, but powder potassium polyacrylate super absorbent ploymer has a great influence on the proportion of superior tobacco.[Conclusion] Potassium polyacrylate super absorbent ploymer with different particle sizes improved the quality of flue-cured tobacco, and the fine granularity potassium polyacrylate super absorbent ploymer had great influence on levels of nicotine, total nitrogen, potassium and chlorine of tobacco, and the powder potassium polyacrylate super absorbent ploymer had a great influence on the total sugar and reducing sugar levels of tobacco. Fine granularity potassium polyacrylate super absorbent ploymer should be used in yellow brown soil in Qinba Mountain area in tobacco fields.