With the aim to explore the influence of plant additive on soil water holding capacity, the soil-water characteristic curves under different soil bulk density, different plant additives and different additive proportions were measured, and the influences of plant additive on the soil water-holding capacity under the conditions mentioned above were analyzed. Then, the soil-water characteristic curves were fitted by using the models of RETC software，and the parameters of the models and the model suitability were determined. The results show that under the same soil water suction, the soil water contents of the treatments with plant additive are higher than that of pure soil; the treatment with 3% maize leaf plant additive has better water conservation capability than the treatment with 3% maize-cob, but the treatments with 1% plant additive have little difference. In the low suction stage, the mixing plant additive reduces the proportion of large pores in the soil; while at the higher suction stage, the plant additive increases the small pores proportion of soil, thereby improves the soil water-holding capacity. The analysis results of model suitability with models of RETC software show that the optimal model of unsaturated hydraulic conductivity is fitting Mualem model. The optimal models of the treatments with 1.35g/cm3 and 1.40g/cm3 soil bulk density are VGM(m,1/n) and VGM(m,n), respectively, with 1% and 3% maize leaf additive, while those are BCM and GM(m,1/n), respectively, with 1% and 3% maize-cob additive.