Abstract: On the basis of geomorphology, lithology, dating and sedimentary environment survey on Quaternary red earth in the field, phytolith analyses show that red earth contains abundant phytolith morphotypes, mainly originating from grasses, broad-leaved and gymnosperm trees. Distribution patterns of phytolith percentage, warmth index and grass cover index demonstrate that there occur 3 assemblage zones in response to palaeo-vegetation and palaeo-climate changes in mid-late Pleistocene, respectively. Correlation of phytolith assemblages and relative indices (C₂₁^-/C₂₂⁺, C₂₃/C₃₀) of molecular fossils indicates that palaeo-vegetation and palaeo-climate are characterized by the alternation of glaciation (arid-cool, weak weathering) and interglaciation (warm-humid, strong weathering) during red earth deposition on an alluvial fan. Due to abundant rainfall and high level of underwater, grasses were common in the surface of alluvial fan during interglaciation.