Based on data of 21 key countries along the“China Europe Railway Express”route from 2006 to 2015, the paper assesses the green investment efficiency and the influencing factors, with the support from SBM-undesirable model and spatial econometric model. Result shows that there exists great untapped potential for investment cooperation among China and the route countries. Moreover, during this period the overall green investment efficiency is not high, but it always maintains an upward trend. The overall green investment efficiency is negatively restricted by the green investment scale efficiency. There is obvious efficiency difference among these countries, some of which have formed stable spatial clusters, even showing trend of gradual expansion. In addition, the green investment efficiency is affected by domestic investment environment. The industrial structure is negatively influencing the green investment efficiency, yet not sustainable. The institutional factor and external dependence factor both show a significant role in promoting the green investment efficiency.