A communication method and apparatus are applied to fields such as V2X, vehicle to everything, an intelligent connected vehicle, assisted driving, and intelligent driving. The method includes: a first terminal device determines a first new data indicator NDI based on an identifier of a first destination address and an identifier of a first hybrid automatic repeat request HARQ process, where the first NDI is included in first sidelink control information SCI, and the first SCI is used to schedule first data; and the first terminal device sends, through a sidelink, the first SCI and/or the first data to a second terminal device.