In the 1920s and 1930s, a trend of reprinting old books emerged in the Chinese publishing industry. Old books with public copyright were regarded as "intellectual goods", and reprinting, sales and circulation of old books were realized through photocopying and printing. On the one hand, it was due to the lack of high-quality publishing resources in modern China and the large profit margin of old books; on the other hand, it was the stimulation and promotion of modern printing technology from engraving to printing. Though this boom was criticized and satirized by some people, triggered the debate of "looking forward" or "going backward", but there is no denying the fact that the large scale old books publishing activities have greatly promoted the "modernization" of Chinese traditional knowledge, preservation, dissemination and promotion of the Chinese traditional culture and classics, and provided food for thought for contemporary people.