Abstract: [Objective]In order to develop the high-productivity technology of forage sweet sorghum in autumn idle land,the association of planting density and line spacing with individual plant productivity was assessed.[Methods]Using split-plot experiment design method and LSD method of IBM.SPSS.Statistics.v22 statistics software,a field experiment was conducted to compare the single plant productivity of the forage sweet sorghum cultured with different planting density and line spacing.[Results]The results showed that planting density and line spacing had important influence on individual plant productivity of forage sweet sorghum in autumn idle land.Moreover,the optimal combination of plant productivity was determined as A1B4 with the planting density of 7.50×104 plants/hm2 and the line spacing of 40 cm.Under this configuration,the fresh and dry weight per plant was 654.37 g/plant and 147.11 g/plant,respectively.[Conclusion]Our results provided a theoretical basis for improving the production of forage sweet sorghum in autumn idle land.