A model test of the composite long-short pile foundation including single pile,three piles,nine piles and fifteen piles was put forward.Design of plan,measured instruments,methods and results about the model test,test results and factors of test error are also provided.The test data shows that the skin friction behavior of the short pile in the composite long-short pile foundation is almost the same as the single pile and that of the long pile is different from the single pile due to the significant effects by the short piles.At the beginning of loading the skin friction along the upper of the long pile does not work.By the end of the ultimate loading the skin friction along the upper of the long pile does fully play its role,the same as that of the single pile.