In order to maximize the capacities of resources constraints in the multiple projects environment, it is firstly necessary to make sure where the resources constraints are, and to schedule them. And then, add a set of time buffer to protect the bottle-neck resources. For some purposes, the project schedule is not easy to be altered in enterprises. Instead of adding a set of time buffer, we use others ways to protect resource constraints and to improve capacities. 4 cases are discussed in this research respectively, and the characteristics in this research contain whether the project plan is announced at the year beginning, whether the number of team members is fixed, and whether the project is outsourced or in-house. The main purpose is to investigate how the enterprises arrange the resources in 3 different periods: the projects at the year beginning, new projects joined during a year , and new demands in the existing projects during a year. The research results show: (1) Enterprises usually recruit employees at the beginning of the year, which prevents from the unqualified human resource as the projects going. (2) The teams with fixed member are allocated members in the projects which are the same domain. It¡¦s not easy to support between projects of different domains in the same team, except IT support. It¡¦s also difficult to support between teams, because the relationship of teams is competitive. (3) In the established team in terms of projects, enterprises assign team members in project which are the same domain by the function. It¡¦s easy to support between members with the same domain. It¡¦s not easy to support between members with different domain, except IT support. (4) Carrying out outsourcing projects in the enterprises, complete project in the different period to explore the resource constraints. (5) Carrying out in-house projects in the enterprise, reduce insignificance project scope or to reschedule insignificance project to explore the resource constraints. (6) Carrying outsourcing and in-house projects in the enterprises, reduce insignificance project scope or to reschedule insignificance project to explore the resource constraints.