A method for determining evaluation time for downlink transmission quality monitoring, the method performed by a terminal device, the method comprising: receiving first indication information from a network device, wherein the first indication information is used to indicate channel occupancy time of the network device on a channel in an unlicensed spectrum to send a reference signal; determining a first quantity based on the first indication information, wherein the first quantity is a quantity of available reference signals in an initial first evaluation time in an unlicensed spectrum, wherein the initial first evaluation time is an initial value of a first evaluation time and is predefined or preconfigured; and determining the first evaluation time by dynamically extending the first evaluation time based on the first quantity and a second quantity, wherein the second quantity is an expected quantity of available reference signals in the first evaluation time to satisfy a precision requirement for quality monitoring, wherein the determining the first evaluation time by dynamically extending the first evaluation time comprises: extending the first evaluation time until the first quantity reaches the second quantity or the first evaluation time reaches an evaluation time threshold, wherein the available reference signal satisfies at least one of the following: a moment of receiving the available reference signal is comprised in the channel occupancy time; a signal-to-noise ratio of the available reference signal is greater than a signal-to-noise ratio threshold; and a receive power of the available reference signal is greater than a receive power threshold. receiving first indication information from a network device, wherein the first indication information is used to indicate channel occupancy time of the network device on a channel in an unlicensed spectrum to send a reference signal; determining a first quantity based on the first indication information, wherein the first quantity is a quantity of available reference signals in an initial first evaluation time in an unlicensed spectrum, wherein the initial first evaluation time is an initial value of a first evaluation time and is predefined or preconfigured; and determining the first evaluation time by dynamically extending the first evaluation time based on the first quantity and a second quantity, wherein the second quantity is an expected quantity of available reference signals in the first evaluation time to satisfy a precision requirement for quality monitoring, wherein the determining the first evaluation time by dynamically extending the first evaluation time comprises: extending the first evaluation time until the first quantity reaches the second quantity or the first evaluation time reaches an evaluation time threshold, wherein the available reference signal satisfies at least one of the following: a moment of receiving the available reference signal is comprised in the channel occupancy time; a signal-to-noise ratio of the available reference signal is greater than a signal-to-noise ratio threshold; and a receive power of the available reference signal is greater than a receive power threshold. a moment of receiving the available reference signal is comprised in the channel occupancy time; a signal-to-noise ratio of the available reference signal is greater than a signal-to-noise ratio threshold; and a receive power of the available reference signal is greater than a receive power threshold.