The hidden terminal problem is particularly common in wireless local networks (WLANs). It is the dominant factor to reduce throughput. In this paper, we develop a new method to improve throughput in WLANs with hidden terminals under the non-saturated condition. The hidden terminal problem may result in very large contention window size, so that much channel resource is wasted. Our method efficiently improves the contention probabilities for the station with very large contention window size. We analyze the performance of the proposed scheme by using Markov chain model. Moreover, we conduct simulation experiments under NS2, and show that our method can efficiently improve throughput performance when compared with the existing 802.11 protocol.