中文摘要：

在不对称信息框架下,建立风险投资短期契约和长期契约的模型,并对其进行了比较研究,最后,得出结论：不对称信息下的长期契约投资水平严格优于短期契约,但都不能达到社会最优投资水平,即风险投资项目都被过早终止;不对称信息对风险投资的社会有效投资水平、长期契约与短期契约投资水平的影响是同方向、同规模的;在不对称信息下,风险投资短期契约的低效率性是刚性的,不能得到改善,而长期契约的低效率性则可以通过提高贴现率、降低项目主观成功概率得到改善,但也不能完全消除。

英文摘要：

We construct a short-term contract model and a long-term contract model of venture capital under asymmetrical information.By comparing the results of the two models,we find that the investment level of the long-term contract is strictly better than that of the short-term contract.However,neither of them can reach the optimal social investment level,since venture capital project is terminated prematurely.In addition,the effects of asymmetrical information on the social effective investment level and the investment levels of both the short-term contract and the long-term contract are all proportional to each other in terms of direction and scale.Under asymmetrical information,on one hand,it is proved that the inefficiency of the short-term contract of venture capital is nonflexible and cannot be improved.On the other hand,the inefficiency of the long-term contract can be improved by raising discount rate or reducing the subjective success probability of the project,while it cannot be eliminated completely.