An acknowledgement information sending method performed by a terminal device, the method comprising: • receiving uplink scheduling information from a network device in a time cell n, wherein the uplink scheduling information is used to: ∘ schedule a physical uplink shared channel of a time cell n+k1, and ∘ obtain a maximum quantity of first downlink data packets allowed to be sent by the network device to the terminal device from a time cell n-k3 to a time cell n+k2, wherein n is a non-negative integer, k1, k2, and k3 are all positive integers, and k2<ki or k2=k1, • receiving first downlink data packets whose quantity is less than or equal to the maximum quantity of first downlink data packets from the network device, the first downlink data packets comprising: o second downlink data packets sent by the network device to the terminal device from the time cell n-k3 to the time cell n, and ∘ third downlink data packets sent by the network device to the terminal device from the time cell n+1 to the time cell n+k2, wherein the uplink scheduling information comprises first indication information, the first indication information is used to indicate a quantity Q2 of the second downlink data packets, • determining the maximum quantity of the first downlink data packets according to the formula: min k2 ′, Q3 − Q2 + Q2, wherein k2' is a quantity of time cells allowed to transmit a downlink data packet from the time cell n+1 to the time cell n+k2, Q3 is a maximum quantity of hybrid automatic repeat request processes that is supported by the terminal device, Q2 is a non-negative integer and Q2 indicates a quantity of the second downlink data packets, and Q3 is a positive integer; and • sending acknowledgement information of the first downlink data packets to the network device on the physical uplink shared channel of the time cell n+k1 based on the determined maximum quantity of the first downlink data packets. • receiving uplink scheduling information from a network device in a time cell n, wherein the uplink scheduling information is used to: ∘ schedule a physical uplink shared channel of a time cell n+k1, and ∘ obtain a maximum quantity of first downlink data packets allowed to be sent by the network device to the terminal device from a time cell n-k3 to a time cell n+k2, wherein n is a non-negative integer, k1, k2, and k3 are all positive integers, and k2<ki or k2=k1, ∘ schedule a physical uplink shared channel of a time cell n+k1, and ∘ obtain a maximum quantity of first downlink data packets allowed to be sent by the network device to the terminal device from a time cell n-k3 to a time cell n+k2, wherein n is a non-negative integer, k1, k2, and k3 are all positive integers, and k2<ki or k2=k1, • receiving first downlink data packets whose quantity is less than or equal to the maximum quantity of first downlink data packets from the network device, the first downlink data packets comprising: o second downlink data packets sent by the network device to the terminal device from the time cell n-k3 to the time cell n, and ∘ third downlink data packets sent by the network device to the terminal device from the time cell n+1 to the time cell n+k2, wherein the uplink scheduling information comprises first indication information, the first indication information is used to indicate a quantity Q2 of the second downlink data packets, o second downlink data packets sent by the network device to the terminal device from the time cell n-k3 to the time cell n, and ∘ third downlink data packets sent by the network device to the terminal device from the time cell n+1 to the time cell n+k2, • determining the maximum quantity of the first downlink data packets according to the formula: min k2 ′, Q3 − Q2 + Q2, wherein k2' is a quantity of time cells allowed to transmit a downlink data packet from the time cell n+1 to the time cell n+k2, Q3 is a maximum quantity of hybrid automatic repeat request processes that is supported by the terminal device, Q2 is a non-negative integer and Q2 indicates a quantity of the second downlink data packets, and Q3 is a positive integer; and • sending acknowledgement information of the first downlink data packets to the network device on the physical uplink shared channel of the time cell n+k1 based on the determined maximum quantity of the first downlink data packets.