How to realize the seamless link between the PC and the Qsys system has always been the focus of a design in the engineering practice. In view of the above problem, this paper presents an IP core design of PCIslave interface based on Avalon bus, which replaces the original design method of using special interface chip, in form of embedded IP core. The design is according to the topdown design process, firstly gives the RTL level module partition of the PCIslave interface, and carefully designs the mealy type of state machine. Then completes the onchip interconnection between Avalon bus and PCI bus. Finally develops an IP soft core with independent intellectual property rights, and validates the feasibility of the design in engineering practice.