Technological diversification is an important prerequisite and foundation for the persistent innovation of high-tech industry, and it is of great value to explore the mechanism of its role. On the basis of reviewing relevant theories, the basic hypotheses of the influence of technological diversification in high-tech industry on persistent innovation, the moderating effect of external technology acquisition and transformation and technological diversification pattern were put forward, and empirical tests were carried out using the panel data of China''s high-tech industry in the period of 1998-2020. The results show as follows. Firstly, the promotion effect of technological diversification on persistent innovation (technology and product) in high-tech industry has a threshold effect and there exists an "optimal interval". Secondly, external technology acquisition and transformation positively moderate the relationship between technological diversification and persistent innovation in high-tech industry. Thirdly, based on the two dimensions of technology relatedness and core technology competence, the technological diversification of high-tech industry can be divided into four patterns: high relatedness - strong core, low relatedness - strong core, low relatedness - weak core and high relatedness - weak core. Fourthly, there are differences in the promotion effect of different patterns of technological diversification on the persistent innovation of high-tech industry. The "high relatedness - strong core" type of technological diversification is more conducive to persistent innovation of technology, the "low relatedness - strong core" type of technological diversification is more conducive to persistent innovation of product, and the "low relatedness - weak core" type of technological diversification has the weakest promoting effect on persistent innovation.