The invention relates to a system for collecting rainwater for salt leaching for slope type saline and alkaline land. The system comprises a rainwater collecting platform perpendicular to a drainage slope and a rainwater collecting trench located on the rainwater collecting platform, wherein geotextiles are laid on side surfaces and the bottom surface of the rainwater collecting trench, a rubble layer is laid at the lower layer of the rainwater collecting trench, a yellow sand layer is laid at the upper layer of the rainwater collecting trench, and a lawn area is laid at the surface layer of the rainwater collecting trench. The system has the beneficial effects that the system is convenient and quick to construct, obvious in effect and low in manufacturing cost, rainwater converged at the upper-part slope surface can be effectively retained with the method, the problem that rainwater in concrete, brick and grouted rubble rainwater collecting trenches infiltrate hardly is solved, meanwhile, problems that earth trenches is not resistant to rainwash and collapse are solved, the problem that rainwater in the slope type saline and alkaline land infiltrate for salt leaching hardly is effectively solved, and the landscape effect is guaranteed through laying of turf.