A data transmission method, comprising: obtaining, by a terminal device, a first indication from a network device, wherein the first indication indicates a first resource, and the first resource is used for a transmission of first system information on an unlicensed spectrum; and receiving, by the terminal device, the first system information on the unlicensed spectrum by using the first resource; wherein the method further comprises: sending, by the terminal device, request information to the network device, wherein the request information is used to request the first system information; and the receiving, by the terminal device, the first system information on the first resource comprises: receiving, by the terminal device on the first resource, the first system information sent by the network device based on the request information; characterized in that receiving, by the terminal device, the system information on the first resource comprises: starting, by the terminal device, a first timer, and attempting to receive the first system information on the first resource during running of the first timer; and the method further comprises: performing, by the terminal device, cell reselection after the first timer times out if the terminal device does not receive the first system information. obtaining, by a terminal device, a first indication from a network device, wherein the first indication indicates a first resource, and the first resource is used for a transmission of first system information on an unlicensed spectrum; and receiving, by the terminal device, the first system information on the unlicensed spectrum by using the first resource; wherein the method further comprises: sending, by the terminal device, request information to the network device, wherein the request information is used to request the first system information; and the receiving, by the terminal device, the first system information on the first resource comprises: receiving, by the terminal device on the first resource, the first system information sent by the network device based on the request information; characterized in that receiving, by the terminal device, the system information on the first resource comprises: starting, by the terminal device, a first timer, and attempting to receive the first system information on the first resource during running of the first timer; and the method further comprises: performing, by the terminal device, cell reselection after the first timer times out if the terminal device does not receive the first system information. sending, by the terminal device, request information to the network device, wherein the request information is used to request the first system information; and the receiving, by the terminal device, the first system information on the first resource comprises: receiving, by the terminal device on the first resource, the first system information sent by the network device based on the request information; characterized in that receiving, by the terminal device, the system information on the first resource comprises: starting, by the terminal device, a first timer, and attempting to receive the first system information on the first resource during running of the first timer; and the method further comprises: performing, by the terminal device, cell reselection after the first timer times out if the terminal device does not receive the first system information. receiving, by the terminal device on the first resource, the first system information sent by the network device based on the request information; characterized in that receiving, by the terminal device, the system information on the first resource comprises: starting, by the terminal device, a first timer, and attempting to receive the first system information on the first resource during running of the first timer; and the method further comprises: performing, by the terminal device, cell reselection after the first timer times out if the terminal device does not receive the first system information. starting, by the terminal device, a first timer, and attempting to receive the first system information on the first resource during running of the first timer; and the method further comprises: performing, by the terminal device, cell reselection after the first timer times out if the terminal device does not receive the first system information.