The invention discloses a multi-probe time division multiplexing device, a flow speed measuring device and a method thereof. The time division multiplexing device comprises the components of a plurality of signal input interfaces which are respectively connected with a probe for receiving multiple analog water current signals that are acquired by a plurality of probes and input a plurality of groups of analog water current signals to an input port of a signal selector according to a preset line grouping rule; a controller which makes the input port of the signal selector connect with an outputport according to a preset conduction rule for conducting a signal channel, and forwards the analog water current signal that is input into the input port to the output port; a signal selector whichcomprises a plurality of input ports and an output port and is connected with the plurality of signal input ports and the signal output port, and through controlling of the controller, realizes conduction of the signal channel for forwarding the analog water current signal which is input into the input port to the output port; and a signal output interface which is connected with the output port of the signal selector and outputs the analog water current signal. The multi-probe time division multiplexing device, the flow speed measuring device and the method thereof can satisfy a requirement for measuring profile flow speeds at multiple points.