The invention relates to a preparation method of Maillard reaction products of ulva fasciata polysaccharide and gelatin peptide. The preparation method comprises the following steps: (1) using clean ulva fasciata as a raw material, obtaining ulva fasciata crude polysaccharide by utilizing ultrasonic auxiliary water extraction and ethanol precipitation technologies, adding water for compounding an aqueous solution, and after performing centrifugal filtration, performing ultrafiltration and separation by sequentially using 10kDa ultra filtration membranes and 100kDa ultra filtration membranes so as to obtain preliminary separated and purified polysaccharide of which the molecular weight is greater than 10kDa and smaller than 100kDa; (2) performing enzymolysis on the preliminary separated and purified polysaccharide with composite enzymes so as to obtain enzymatic products; (3) compounding the enzymatic products into an aqueous solution, filtering the aqueous solution so as to obtain filtrate, performing ion column chromatography through a DEAE-Sepharose Fast Flow ion column chromatography system and performing gel column chromatography through a Sephadex G-25 gel chromatography system on the filtrate so as to obtain polysaccharide enzymatic substances; (4) performing enzymolysis on gelatin with basic protein enzymes so as to obtain gelatin peptide; and (5) performing a Maillard reaction for 0.5-3 hours on the polysaccharide enzymatic substances and the gelatin peptide in distilled water under the conditions that pH is 6.5-7.2 and the temperature is 70-100 DEG C so as to obtain the Maillard reaction products, wherein the Maillard reaction products have favorable antioxidant activity.