A communications system, comprising: a first group management functional entity and a second group management functional entity, wherein the first group management functional entity is configured to receive a group regrouping creation message from first user equipment, UE, wherein the group regrouping creation message comprises identifiers of N mission critical push to talk, MCPTT, groups, and the group regrouping creation message is used to request to create, according to the identifiers of the N MCPTT groups, a temporary group which is initiated by a first MCPTT user and into which the N MCPTT groups are regrouped; the first group management functional entity is a group management functional entity in a home network of the first MCPTT user; and the first MCPTT user belongs to at least one MCPTT group of the N MCPTT groups, and the first UE is a UE used by the first MCPTT user; the first group management functional entity is further configured to send the group regrouping creation message to the second group management functional entity, wherein the second group management functional entity is any group management functional entity that manages at least one MCPTT group of a first MCPTT group, wherein the first MCPTT group is not an MCPTT group managed by the first group management functional entity, and the first MCPTT group is at least one MCPTT group of the N MCPTT groups; the second group management functional entity is configured to send a group regrouping response message to the first group management functional entity; and the first group management functional entity is further configured to configure information about the temporary group according to the group regrouping response message. the first group management functional entity is configured to receive a group regrouping creation message from first user equipment, UE, wherein the group regrouping creation message comprises identifiers of N mission critical push to talk, MCPTT, groups, and the group regrouping creation message is used to request to create, according to the identifiers of the N MCPTT groups, a temporary group which is initiated by a first MCPTT user and into which the N MCPTT groups are regrouped; the first group management functional entity is a group management functional entity in a home network of the first MCPTT user; and the first MCPTT user belongs to at least one MCPTT group of the N MCPTT groups, and the first UE is a UE used by the first MCPTT user; the first group management functional entity is further configured to send the group regrouping creation message to the second group management functional entity, wherein the second group management functional entity is any group management functional entity that manages at least one MCPTT group of a first MCPTT group, wherein the first MCPTT group is not an MCPTT group managed by the first group management functional entity, and the first MCPTT group is at least one MCPTT group of the N MCPTT groups; the second group management functional entity is configured to send a group regrouping response message to the first group management functional entity; and the first group management functional entity is further configured to configure information about the temporary group according to the group regrouping response message.