Abstract: To improve the cracking resistance of concrete for railroad bed slabs, natural modifiers (WTL-E and KTL-E) that can improve mechanical properties and crack resistance of concrete were prepared from wax tree leaves and kiwi tree leaves. Indoor one-factor comparative tests were carried out, and concrete compressive strength and splitting tensile strength tests were performed to study its mechanical properties, and the optimal concrete ratio was determined. Concrete plate shrinkage and annular confinement shrinkage tests were designed to investigate the effect of modifiers on the cracking properties of concrete. The internal evolution mechanism of concrete was analyzed in conjunction with microscopic characterization techniques. The results show that KTL-E has less surface tension than WTL-E, and its modified concrete also exhibits better mechanical properties and crack resistance. The best concrete modification effect is achieved when the KTL-E admixture is 2.8% and fly ash is 20%. Compared with plain concrete, the compressive strength, splitting strength and cracking time increase by 9.46%, 7.80% and 52.78% respectively, which effectively improve the cracking resistance of concrete. The research results can provide a theoretical basis for the development of green admixtures that can improve the crack resistance of concrete.