The numerical calculations by using new material constants were in good agreement with the experimental results of the temperature-related SAW properties on the langasite substrate with Euler angle (0°, 140°, qq). The temperature-related SAW properties as a function of the metal thickness of IDT were also experimentally investigated. It was revealed that a thicker metal leads to a lower turnover temperature. Furthermore we investigated the NSPUDT (natural single phase unidirectional transducer) properties of langasite with Euler angle (0°, 140°, 25°) experimentally. Its directivity was almost equal to one estimated by the calculation based on Coupling of Mode (COM) model. This NSPUDT property is a promising feature for the low-loss IF filter.