This paper introduces the design method of a surface acoustic wave filter for electronic toll collection system (ETC). The filter adopts 3-1-3 segment capacitance-weighted structure and electrode width control(EWC) transducer unit structure. The substrate material is 128°Y-X lithium niobate. Through optimizing the filter peripheral matching inductance, the transducer reflection finger structure and film thickness, we design a filter with center frequency of 40 MHz, small insertion loss of -7.5 dB and high stopband suppression. Breaking through the conventional surface acoustic wave filter design method for the first time, the design method of the transducer full withdraw weighting in the fan-shaped structure is adopted, and the finally fabricated devices meet the use requirements of ETC project.