The invention provides a transparent and high-heat-resistant cycloolefin copolymer and a preparation method thereof. By selecting a specific structure, a vitrification transition temperature of the cycloolefin copolymer is precisely adjustable, the range is 105 to 169 DEG C, a solution is used for forming a coating, a material light transmittance can reach up to 91 percent, a tensile test shows that the material has excellent mechanical performance, the tensile strength is between 25MPa and 50MPa, the tensile modulus is 1600MPa to 2800MPa, the elongation at break is 2.5 to 5.4 percent, 10 percent of thermal decomposition temperature is greater than 410 DEG C, and the heat stability is good. According to the preparation method provided by the invention, by selecting a specific catalyst, the catalytic conversion rate can reach 100 percent, and the side reaction such as cross linking does not occur; and moreover, no promoter is needed, the polymerization tolerance is good, the distribution of molecular weights is adjustable, and the application prospect is good.