The invention discloses a hydrothermal-resistant composite and a preparation method of the composite, in particular to a cyanate ester (CE)/micro encapsulant composite and a preparation method of the composite, belonging to the high performance resin matrix composite field. The mass ratios of the CE/micro encapsulant composite are 100 portions cyanate ester, 0 to 5 portions epoxy resin, 2 to 30 portions epoxy resin micro encapsulant, 0 to 600 portions fiber. The preparation method is characterized in that: the epoxy resin micro encapsulant coated by polyurea formaldehyde is filled into the CEto prepare CE/micro encapsulant resin system, and then the CE composite with high hydrothermal-resistant performance is obtained. The hydrothermal-resistant composite has the advantages that: compared with the CE system without micro encapsulant, the hydrothermal-resistant performance of the CE/micro encapsulant composite is improved greatly. The CE/micro encapsulant composite can be used for preparing printed circuit boards for high-speed digital and high frequency, high performance composite in aerospace.