This paper proposes a novel auction-based mechanisms named Decreasing Cancellation Fee Auction (DCFA) for task allocation in the environment where a service provider has finite capacities and consumers could withdraw their bids. We consider a new type of auction called the refundable auction, i. e. refund means that a consumer’s showing up is uncertain and he can get back partial of his payment if his cancellation or no-show occurs. This mechanism can boost seller revenue, satisfy incentive compatibility, individual rationality and still hold a high efficiency.