The invention discloses a preparation method of a solid acid Fenton catalyst for processing methyl orange waste water, comprising the following steps: a, using granular starch, glucose or beta-cyclodextrin as raw material, adding concentrated sulfuric acid for carbonization at the temperature of 120 DEG C; b, cooling the carbonized material to room temperature, then washing; c, drying and grinding; d, adding active components for dipping, then washing; e, drying the obtained solid for 8-10h at the temperature of 110 DEG C; and f, after drying, roasting at the temperature of 300-700 DEG C, cooling to room temperature to obtain the corresponding solid acid heterogeneous Fenton catalyst. The prepared catalyst solves the problems of loss of active components, large liquid acid consumption, low utilization rate of H2O2, equipment corrosion, environmental pollution seriously and the like in traditional heterogeneous Fenton catalytic oxidation process, and is a green and high effective organic substance degraded Fenton catalyst.