Hydraulic transmission and control technology is a core supporting technology for agricultural machinery. Its technical performance directly determines the operation quality, production efficiency, and overall reliability of agricultural machinery. This paper focuses on hydraulic transmission and control technology for agricultural machinery. It systematically reviews the field from three dimensions: key technology analysis, research status review, and development trend outlook. First, it elaborates the three core technical systems in agricultural machinery hydraulics. In terms of hydraulic components, it analyzes the working principles and application scenarios of power elements, actuating elements, and control elements. In terms of hydraulic systems, it analyzes the technical characteristics and evolution paths of five typical systems used in agricultural machinery. In terms of control technology, it summarizes a multi-level technical framework. This framework includes classical PID and its improved algorithms, advanced control methods, and intelligent control methods. Second, based on the latest domestic and international research literature, it comprehensively reviews the research progress in hydraulic components, hydraulic systems, and control methods. Finally, in response to the transformation and upgrading of smart agriculture and the “dual carbon” strategy, it identifies three major future directions for hydraulic transmission and control technology in agricultural machinery. The findings of this review are expected to offer theoretical references and technical guidance for the R&D and industrial upgrading of high-end hydraulic systems for agricultural machinery.