A simple RSPUDT filter is composed of two SPUDT interdigital transducers (IDT), and SAW resonates between the two IDTs. To improve designing flexibility and more importantly to reduce chip size, reflective gratings were added between the two IDTs. It is the reflective gratings that increase the effective length of SAW transmission, so that using the new structure the chip size can potentially reduced by a factor two. This structure was adopted in this paper, by which RSPUDT SAW filter was deisgned. The measurement accorded well with simulation results.