In this paper, a wide stopband bandpass filter using source-load coupling technique is proposed. With the source-load coupling structure, multiple transmission zeros are generated to suppress the harmonic responses in the stopband. By adjusting the gap space between the input/output feed lines, the locations transmission zeros can be controlled. Moreover, the open stub of the input/output feed lines are also used to generate transmission zeros in the stopband. In this design, stepped-impedance resonators (SIR) are utilized to minimize the overall circuit size and control the harmonic frequencies. The impedance and length ratios of the SIR are determined to move its first harmonic to a higher frequency. The center frequency of the filter is 2.45 GHz, and the stopband rejection is higher than 30 dB from 2.9 GHz to 13.36 GHz.