Combinatorial auction, one of most popular market mechanisms, is well-known mechanism for effective resource allocation to self-interested agents. In real scenarios, since the auction mechanism has to clear the market very frequently, actually there is not enough time to compute exact optimal winners. In this paper we show that some approximation algorithms provide sufficient quality of winners for auctions that have large number of bids but have hard time constraints. Furthermore, we compare and discuss about desirable properties of such approximation algorithms to be embedded in application systems.