Abstract: Wellsite nuclear magnetic resonance (NMR) technologies have developed rapidly in the past 20 years and have played an important role in oil and gas drilling and exploitation. They refer to the NMR measurement, analysis, and application carried out in complex and harsh environments of oil and gas drilling sites, which involve multiple aspects such as basic theory, measurement instruments, data acquisition and processing, and interpretation and application. In the past decades, Chinese scientists and researchers have made continuous efforts to tackle the challenges, going through the development course of “introduction, absorption, integrated innovation, and initial innovation.” As a result, the NMR measurement and analysis technologies suitable for continental oil and gas are developed and industrial applications are achieved, and rich technical reserves are formed in several novel and forward-looking fields. This paper systematically summarized the development course of wellsite NMR theory, methods, instruments, and technologies in and outside China as well as the key breakthroughs in these aspects. On this basis, it gave the application prospects and challenges of wellsite NMR technologies in the exploration and development of complex oil and gas and shale oil and gas. The research is expected to promote the exploration and development level and progress of shale oil and gas and deep complex oil and gas in China.