Actively promoting synergies between forest carbon sinks and biodiversity conservation is an important initiative for the world to cope with climate change and curb biodiversity loss. Based on the synergy theory, this paper clarifies the driving mechanism of the synergy between forest carbon sinks and biodiversity conservation, analyzes the dilemma faced by the synergy between the two, and proposes an implementation strategy to solve the dilemma. It is found that the driving mechanism of the synergy between forest carbon sinks and biodiversity conservation is twofold: firstly, the development of forest carbon sinks has significant direct and indirect, positive and negative effects on biodiversity, which makes it difficult to separate the two from each other and develop independently; and secondly, biodiversity conservation provides new opportunities for the sustainable development of forest carbon sinks. However, due to the difficulty of realizing the value of biodiversity conservation products alone, the high degree of regional overlap, but the main body of the project has not been coordinated and unified, and the development of forest carbon sink projects is prone to damage biodiversity, etc., resulting in the synergy of the two facing price "failure", the main body "disconnection", and the result of "failure". As a result, the synergy between the two is faced with three major realities: price "failure", subject "disconnection", and process "inappropriate". For this reason, we should take "forest carbon sinks +" as the core concept, embed biodiversity protection in the form of "private goods" in the carbon sink market, and promote the main body of transactions in the forest carbon sink market to expand into "carbon sinks + biodiversity protection" dual subjects, forming a forest carbon sink market. To promote the expansion of forest carbon sinks market trading subjects into "carbon sinks + biodiversity protection" double subjects, to form the biodiversity protection synergy in all aspects of forest carbon sinks project development, and to realize the synergistic development and integrated development of forest carbon sinks and biodiversity protection.