Abstract: Current task placement algorithms for homogenous architectures are inapplicable to the reconfigurable device with multifarious resources, which are not conducive to the practical application.Models of device and hardware tasks with heterogeneous architecture are built to deal with constraints on the location of hardware tasks, which are caused by static cells such as BlockRAMs distributed on the reconfigurable device.This paper proposes an online task placement algorithm based on relative task coverage.The algorithm establishes a placement window for task queue, and places the foremost task according to the relative task coverage generated by all tasks in the placement window.Therefore, the placement of subsequent tasks is taken into consideration and the whole efficiency of placement is increased.The experimental results show the algorithm can gain less average waiting time for tasks and higher utilization ratio of device than those of First Fit algorithm.