The invention relates to a cake modifying agent. The cake modifying agent comprises, by weight, 3-20% of emulsifying agent, 2-15% of thickening agent, 65-94.9% of food raw materials, and 0.1-2% of enzyme preparation, wherein the emulsifying agent is one or more of single/double-glycerin fatty acid ester, sucrose fatty acid ester, sodium caseinate, and polyglycerin fatty acid ester; the thickening agent is one or more of hydroxypropyl di-starch phosphate and xanthan gum; the enzyme preparation is one or more of maltogenic amylase and alpha-amylase. The cake modifying agent is suitable for being applied to black rice cake manufacturing, the water-prevention and moisture-retaining performance of the black rice cake can be intensified, the ageing problem like product spalling and scaling are postponed, and thus soft, delicate and wet mouthfeel of the cake is maintained.