This paper investigates the problem of routability prediction in a FPGA that employs a hierarchical routing architecture. Such a FPGcl is called a hierarchical FPGA(HFPGA). A novel model is proposed to analyze various HFPGA configurations. A software tool has been developed to predict the routability of circuits on specific HFPGx4 architectures. Primary contribution of this work is that routability prediction can be done immediately after the technology-mapping step, rather than after placement. The effect of connection block and switch block flexibility on routability is also studied. The results show that compared to a symmetrical FPGA architecture, we can achieve the same degree of routability on a HFPG-4, with much fewer routing switches