Disclosed are a random access method and a network device, and a terminal device. The method includes: a terminal device sending first information on a first resource, and sending second information on a second resource; the terminal device detecting third information on one group of third pre-allocated resources in a first window, wherein a start position of the first window comprises: a position after a first time interval after the terminal device sends the second information; or a first time unit after the first time interval after the terminal device sends the second information; or a first time unit in the one group of third pre-allocated resources after the first time interval after the terminal device sends the second information; and the terminal device receiving fourth information on a fourth resource.