RSS-based device-free localization (DFL) is a very promising technique which allows localizing the target without attaching any electronic tags in wireless environments. In cluttered indoor environments, the performance of DFL degrades due to multipath interference. In this paper, we propose a multichannel obstructed link detection method based on the RSS variation on difference channels. Multichannel detection is proved to be very effective in multipath environments compared to the single channel detection. We also propose a new localization method termed as robust weighted least square (RWLS) method. RWLS first use spatial property to eliminate the interference links and then employ WLS method to localize the target. Since the spatial detection relies on the unknown position of the target. A coarse position estimation of target is also presented. RWLS is robust to interference links and has low computation complexity. Results from real experiments verify the effectiveness of the proposed method.