Terrestrial carbon cycle is one of the vital processes in biogeochemical cycle. Carbon use efficiency (CUE), which is defined as the ratio of growth over total C uptake for organisms, is one of the important parameters in studying carbon flux and carbon distribution patterns. CUE is a quantitative indicator reflecting the carbon assimilation capacity and carbon sequestration potential and can predict carbon feedbacks among the organisms and abiotic environment effectively. However, there are few studies on the CUE, especially the systematic and comprehensive discussion of CUE and its impact factors. We reviewed research methods and developments of carbon use efficiency, compared connections, similarities and differences between CUE_a (the carbon use efficiency of plant) and CUE_h (the carbon use efficiency of microbe). Then, we provided several suggestions for future research:(1) optimizing measure and calculation methods, adjusting parameters based on the local conditions, and combining model methods with the measured data to make CUE's results more accurate; (2) combining CUEs at different scales such as individual, population, community and ecosystem, which can be used to explore the similarities and differences of CUE at different spatial and temporal scales, and provide a new idea for carbon cycle and carbon circulation; (3) studying the responses of CUE to global changes (such as high temperature, drought and CO₂ enrichment), revealing the response and adaptation mechanisms of CUE to global changes; (4) exploring influences of the biological richness and diversity gradients on CUE, explaining the impacts of species diversity reduction or extinction on carbon cycle processes, and linking species diversity with ecosystem functions; (5) strengthening CUE_h research and separating its similarities and differences from CUE_a, combining the CUE_a and CUE_h to explain the carbon distribution and flux characteristics of above- and below-ground parts. At the same time, the research of animal CUE should be carried out appropriately because of rare information of this type of CUE.