A microfluidic channel and a preparation method and an operation method thereof. The microfluidic channel includes: a channel structure, including a channel for a liquid sample to flow through and a channel wall surrounding the channel. The channel wall includes an electrolyte layer made of an electrolyte material; and a control electrode layer, at a side of the electrolyte layer away from the channel. The control electrode layer overlaps with the electrolyte layer with respect to the channel.