•Superharmonic synchronization in micromechanical resonator is utilized for the first time in the MEMS frequency multiplier.•121-order ultra-high frequency amplification is achieved with the improvement of frequency stability and SNR.•A novel frequency automatic tracking system is realized to expand the working range of the designed frequency multiplier. Display omitted Frequency multipliers are widely present in electronic system, which always cooperates with low frequency local oscillator for delivering an output wave with a frequency that an exact integral multiple of the input frequency. Conventional frequency multiplier such as step recovery diode, field-effect transistors, low spurious harmonic, etc., usually has only two or three low multiplication factor. Multi-stage frequency doublers can accumulate the multiplication factor, however, has high power consumption and negative conversion gain. Here, we proposed a novel frequency multiplication mechanism utilizing superharmonic synchronization (SHS) effect in micromechanical resonator. We achieved up to 121th ultra-high frequency amplification with frequency stability of output signal 92 times improved and signal to noise ratio 20% increased. To solve the limitation of narrow synchronization range, a frequency automatic tracking system is designed to expand the working range from 0.62 Hz to 27.5 kHz. The proposed frequency amplification is a promising candidate for frequency multipliers and provides an alternative mechanism for micromechanical sensing and signal processing system.