作为金融市场摩擦之一的代理问题可能导致非效率的企业投资融资决策,本文在企业进行扩张投资和债务融资的基础上,构建动态委托代理模型.首先基于管理者不可观测的努力和储蓄行为进行最优合同设计,利用鞅方法得到了管理者价值函数满足的随机微分方程,并在此基础上给出合同激励相容下价值函数均衡演变的充分必要条件.其次,运用随机控制方法,推导企业价值满足的微分方程,同时给出了合同的解及最优投资触发水平满足的条件.最后,讨论在不同融资情形下,合同预定努力程度随企业现金流变化的不同趋势,给出相应解释,并指出相关参数与最优投资触发水平及企业价值之间的变动关系. As one of the financial market friction agency problem may lead to inefficient business investment financing decision-making, this article in the enterprise expansion investment and debt financing on the basis of the construction of dynamic principal-agent model.First, based on unobservable managers and savings behavior Optimal contract design, the stochastic differential equation satisfied by the manager’s value function is obtained by the martingale method, and on the basis of which the necessary and sufficient conditions for the equilibrium evolution of the value function under the contractual incentive are given.Secondly, using the stochastic control method, The differential equation of value satisfaction is given, and the condition of the contract solution and the optimal investment triggering level are given.Finally, the different trends of the contractual reservation effort with the cash flow of the firm under different financing situations are discussed, and the corresponding explanations are given, And point out the relationship between the relevant parameters and the optimal investment trigger level and enterprise value.