中文摘要：

工程变更是导致BT项目回购总价款大幅增加的关键因素之一,政府有必要通过合理风险分担预设良好的事后支持制度,改善BT项目变更管理的效率和效果.首先,分析BT项目中的两级合同关系；然后,通过分析深圳地铁5号线BT项目合同（A合同）和2007版《标准施工招标文件》第四章“合同条款及格式”组成的两级合同关系,得出引发BT项目工程变更的风险在BT项目发起人、投资人和承包商三方之间的初次分担清单；最后,通过分析深圳地铁5号线BT工程补充合同（B03合同）,得出引发工程变更风险的再分担结果及其实施方案,并将两次风险分担结果进行对比分析.

英文摘要：

Engineering alteration is one of the key factors that result in the lump-sum price of buy-back under the BT mode. Therefore, it is necessary for the government to preset the post-supporting system through proper risk allocation in order to improve the efficiency and the effect of the engineering alteration management under the BT mode. The two-level contract relatinnship is analyzed first in this paper. Then a two-level contract relationship, including the BT contract of Shenzhen metro Line 5 and the contract clauses in Standard Construction Bidding Document （2007 version）, is analyzed to obtain the detailed list of first risk allocation about the engineering alteration risk in BY projects, i.e., the engineering alteration risks undertaken by the sponsor, investor and contractor respectively. At last, the risk reallocation result about the engineering alteration risks of Shenzhen metro Line 5 is studied through its contract supplement and it is also compared with the first risk allocation result.