A keyboard assembly includes a chassis formed with a plurality of cavities, a key unit including a plurality of key modules, and a scanning unit. Each key module is mounted in a respective one of the cavities, and has an individual resonant frequency. The scanning unit emits a detecting signal repeatedly, where a frequency of the detecting signal in each repetition being a different one of a plurality of scanning frequencies. The scanning unit and the key modules are configured such that, for each key module, when the frequency of the detecting signal is one of the scanning frequencies that matches the individual resonant frequency of the key module, the key module reaches electromagnetic resonance and the scanning unit acquires a response signal corresponding to the key module in response to the electromagnetic resonance.