Light use efficiency (LUE) refers to the efficiency of fixed energy to intercepted energy, which is defined as ratio of productivity to intercepted energy. LUE model could simulate LUE and productivity, which is of implication to the simulation and prediction of carbon cycle, productivity and its greatest potential. The uncertainty of LUE model increased under the influence of global change and human activities which has become big challenge to the evaluation of vegetation productivity and carbon cycling. Thus, a systematic analysis of uncertainty and its causes was conducted to improve the estimation and prediction of vegetation productivity. The analysis indicated that the accuracies of LUE models ranged from 62% to 70% with a large variation (32%). The error of model varied with vegetation types, temporal scales and regional difference. The calculation of LUE in LUE model was the key of model uncertainty, which mainly resulted from unclearness of relation between LUE and its influence factors, particularly water. Firstly, it is not clear how different water indexes affected the LUE. Secondly, the spatiotemporal evolvement of relation between influencing factors and LUE has not been simulated rightly. The important research direction in this field is to determine the relationship between the LUE and water and the spatiotemporal evolution pattern of this relationship. Also, it's important to develop the integrated experimental techniques and research methods at plot and regional scales.