Computer aided CAD system plays an important role in urban planning and heritage conservation. When developing new products, the computer aided system can effectively identify the existing CAD model, facilitate reuse for design, thus shortening the development cycle, reducing the development cost, and improving the development e ciency. Therefore, this paper proposes a concept of computer learning algorithm and a model of naive Bayesian algorithm, that is, urban cultural heritage is an important carrier of human history and culture. After long-term development and accumulation, the current form and spiritual signi cance have evolved. Since the reform and opening up, China's urban heritage protection has also achieved fruitful results and valuable experience, thus forming a three-level protection system of famous cities, famous streets and cultural protection buildings. With the continuous maturity of computer aided CAD system theory in the eld of urban heritage, CAD system has deepened the understanding of "culture" in heritage, and the practice of heritage protection has gradually shifted from traditional urban architecture protection to anthropology, cultural geography and other humanities and social sciences. At this stage, computer aided CAD urban planning introduced the integrity, diversity and development oriented sustainable development of heritage protection, and paid unprecedented attention to the local nature of heritage or the special background of heritage generation. The focus on urban heritage protection has shifted from simply proposing protection practices to the power and interest mechanism behind heritage protection. Only in this way can heritage management truly maintain sustainable development.