Electromagnetic interference (EMI) is an inevitable issue in power electronics applications. Although many kinds of solutions have been presented to attenuate EMI noise, there is still little research about the EMI suppression scheme utilized in multimode primary-side regulation (PSR) flyback converters. Targeting EMI regulation in multimode PSR flyback converter, a combo EMI suppression scheme comprised of frequency modulation and dual-slope gate driver is adopted to meet stringent EMI requirements, simplifying peripheral components and design of EMI filter. The proposed scheme is implemented in $0.18~\mu$ m 5/40 V BCD process and occupies a die size (with pads) of $1.05\times 0.8$ mm2. The experimental results show that the conducted EMI waveforms with line/neutral polarity can easily comply with regulations. The deviations of the output voltage are within ±1.3% under different inputs and loads while the peak effciency of 90% is achieved.