Abstract：Substrate，which is the most important material in eco-engineering for rock slope protection(EERSP)，is the substance basis for stable growth of vegetation. The function of substrate relies on the effects of functional materials under condition of limited substance. The primary functional materials，including straw fiber，polyacrylamide(PAM) and super absorbent polymer(SAP)，are investigated quantitatively with functional effects. The results show：straw fiber can keep the stability of substrate by improving the shear strength of substrate，delaying the time of cracking，reducing crack width，and decreasing sediment loss from erosion. However，it is disadvantageous to add too much straw fiber. PAM can improve the precipitation infiltration of substrate，delay runoff time，decrease runoff volume on slope，and increase water stable aggregate content，therefore，improve the anti-erosion capacity of substrate. In addition，the porosity of substrate will be enhanced simultaneously to make the structure of substrate loose and maintain favorable infiltration and air penetrability for promoting vegetation growth. Nevertheless，the effect of PAM，which has significant temporal scale influence and decreases with time，is constrained to certain amount. Appropriate SAP can improve water sucking capacity of substrate，enhance available water content，restrain evaporation，delay wilted point time，and raise anti-drought capacity remarkably. But the course of suck-release can not be reused without limit. The vegetation growth is retarded when excessive SAP is applied to substrate. Under experimental condition，the favorable amount of sucking straw fiber，PAM and SAP is about 4 kg/m2，10 g/m2 and 80 g/m2，respectively.
