The invention relates to a composite filler for an environment-friendly wholly-plastic type plastic runway and a preparation method thereof. The filler is formed by compounding organically modified inorganic fillers. The preparation method is a chemical modification method. The technical solution aims to improve the resilience of the plastic runway and reduce the migration rate of a plasticizer, and introduces long fatty chains and polyurethane chain segments into the inorganic fillers by using the chemical modification method, thereby greatly improving the compatibility and stability of the filler and the plasticizer and the compatibility and stability of the filler and a polyurethane body material.