[Objective] The effects on the hydrological and ecological environment, after the needle-leaved trees inserted into the the broad-leaved forests at steep slope of the dam area, were studied in order to provide a scientific basis for afforestation and improvement of hydrological and ecological environment.[Methods] Three typical vegetation types in the study area were used as research objects, and the hydrological and ecological effects of litter layer and soil layer were quantitatively determined by indoor immersion method and ring knife method.[Results] ① The accumulation of litter was in the order of Pinus tabuliformis-Apricot mixed forest > Mountain apricot forest > Spiraea shrub; the effective storage capacity was in the order of Pinus tabuliformis-Apricot mixed forest > Mountain apricot forest > Spiraea shrub. There was a good functional relationship between the water holding capacity of litter and the water holding rate of litter and the water immersion time. ② The effective water holding capacity of the 3 planting types was Pinus tabuliformis-Apricot mixed forest (69.00 t/hm²)>Mountain apricot forest (60.87 t/hm²)>Spiraea shrub (55.60 t/hm²); The initial infiltration rate of Pinus tabuliformis-Apricot mixed forest was 29.78 mm/min, and the minimum infiltration rate of Spiraea shrub was 22.38 mm/min. The infiltration rate and infiltration time of three planting types had better power(R²>0.97).[Conclusion] Combining the water holding capacity of the litter layer and the soil layer, it could be seen that the water conservation function of the Pinus tabuliformis-Apricot mixed forest was the strongest among the three different vegetation types, while the water conservation capacity of the Spiraea shrub was the worst. It indicated that broad-leaved forest transformation had enhanced the water conservation capacity of forests and improved the hydrological and ecological environment of forests in the steep slope area. Therefore, from the perspective of enhancing water conservation, it was recommended to introduce appropriate density of Pinus tabuliformis in shrubs and broad-leaved forests in the area to improve the hydrological ecological environment of the area.