Abstract: To solve the screen erosion problem of horizontal wells in sand producing gas reservoirs, this paper took the commonly used composite precision screen with multi-layer mesh filter as the research object to carry out experimental study on screen erosion damage mechanism and law through gas carrying sand by using the innovatively developed simulation experimental system of screen erosion in closed space of horizontal well. The experimental results show that the erosion damage of the composite screen with multi-layer metal filter under the condition of gas carrying sand include two mechanisms, i.e., gnawing of frontal protective cover and erosion damage of side filter. The outer protective cover of staggered punching and sewing type has stronger erosion resistance in the front side, but extremely weak one in the lateral side. The erosion damage velocity of the medium at the metal filter is about 2-3 times that at the outer protective cover. In addition, a new structure of two-layer arc like, staggered and complementary punching and sewing type was put forward based on erosion mechanism, and a method for identifying the high erosion risk positions of horizontal wells in heterogeneous gas reservoirs and an optimization design method to improve the erosion resistance of the whole string by hierarchy and stage were researched and constructed. The new outer protective cover with high erosion resistance and the hierarchical and staged design method provide a simple and easy solution for the erosion damage of sand control completion string of horizontal well in high-yield sand producing gas reservoirs while giving consideration to the economics, which can improve the service life and development effect of sand control completion string in gas reservoirs to some extent.