An acknowledgement information receiving method, comprising: obtaining, by a first communications device, a first resource and a second resource; sending, by the first communications device, first control information and first data to a plurality of second communications devices in a group using the first resource, wherein the first communications device and the plurality of second communications devices in the group belong to a first communications device group, the first communications device and the plurality of second communications devices in the group each have a group identifier of the first communications device group, and the first control information is used to indicate the first resource, the second resource, and the group identifier of the first communications device group; receiving, by the first communications device, acknowledgement information from at least one second communications device in the group using the second resource, wherein the acknowledgement information is used to feed back whether a second communications device correctly receives the first data,, wherein the acknowledgement information is negative acknowledgement NACK information; determining, by the first communications device, whether to perform group cast retransmission based on a preset threshold and a ratio of a quantity of pieces of the NACK acknowledgement information to a quantity of communications devices other than the first communications device in the first communications device group; and if the ratio is higher than the threshold, performing group cast retransmission, by the first communications device, by retransmitting the first data to the plurality of communications devices in the group. obtaining, by a first communications device, a first resource and a second resource; sending, by the first communications device, first control information and first data to a plurality of second communications devices in a group using the first resource, wherein the first communications device and the plurality of second communications devices in the group belong to a first communications device group, the first communications device and the plurality of second communications devices in the group each have a group identifier of the first communications device group, and the first control information is used to indicate the first resource, the second resource, and the group identifier of the first communications device group; receiving, by the first communications device, acknowledgement information from at least one second communications device in the group using the second resource, wherein the acknowledgement information is used to feed back whether a second communications device correctly receives the first data,, wherein the acknowledgement information is negative acknowledgement NACK information; determining, by the first communications device, whether to perform group cast retransmission based on a preset threshold and a ratio of a quantity of pieces of the NACK acknowledgement information to a quantity of communications devices other than the first communications device in the first communications device group; and if the ratio is higher than the threshold, performing group cast retransmission, by the first communications device, by retransmitting the first data to the plurality of communications devices in the group.