Lithium-sulfur battery is a promising energy storage device due to its high theatrical capacity and environmental benignity. However, the rapid performance degradation associated with the so-called "shuttle effect" during the charge-discharge process in a typical lithium-sulfur battery greatly limits its practical application. Modification of the separator in a lithium-sulfur battery is an effective approach to alleviate the "shuttle effect". Here, we report a facile method to generate a novel SnO2 functionalized separator to tackle the problem of polysulfide shuttling. We show that the functionalized separator has a neglectable weight/volume increase compared to the pristine separator, which is important for the maintenance of a high energy density of the battery. The functionalized SnO2 serves as a multi-functional layer that improves the performance of the battery. On one hand, the SnO2 layer enhances the compatibility and wettability between the separator and electrolyte, and thus promotes the transfer of Li+. On the other hand, the strong physical/chemical interaction between SnO2 and polysulfide ions helps to suppress the migration of polysulfide effectively. As a consequence of these features, lithium-sulfur battery assembled with SnO2 functionalized separator shows excellent cycling stability and improved rate performance.