In this study, bacterium Pseudomonas sp. strain D was proved to be the main partner assisting Chlamydomonas reinhardtii in improving photolysis-mediated H-2 production and a good partner for promoting H-2 production by the green algae Chlorella and Scenedesmus. In strain D partnered algal-bacterial co-culture, the relative O-2 content in the headspace plus the dissolved oxygen in the culture medium were rapidly consumed by bacterial growth, resulting in a completely anaerobic environment that proved suitable for the activation of algal hydrogenase. Moreover, algal-bacterial cooperation was able to slow the reduction of chlorophyll, enhance starch accumulation, and maintain protein content, which are the potential factors whose control provides an opportunity for improving algal H-2 production. This study systematically analyzed the main pathway responsible for H-2 production by algal-bacterial cooperation and the potential mechanisms for improvement, and proposed an efficient and durable algal-bacterial cooperation system for improving photolysis-mediated H-2 production by green algae.