A channel state information, CSI, measurement method in a communication system according to the IEEE 802.11 standard, wherein the method comprises: sending, by a CSI request apparatus, a first channel state information request CREQ frame, wherein the first CREQ frame is a first public action frame, and comprises at least one group of session parameters that the CSI request apparatus expects to use, the first CREQ frame is used to request a CSI response apparatus that receives the first CREQ frame to determine, in the at least one group of session parameters, a group of session parameters used to transmit a channel state information sounding CS frame, and the CS frame is used by the CSI request apparatus to perform channel state measurement; wherein each group of session parameters of the at least one group of session parameters comprises a transmission parameter and a scheduling parameter; the transmission parameter comprises one or more parameters of a physical-layer protocol data unit, PPDU, format of the CS frame, or channel information, a transmission bandwidth, a modulation and coding scheme, or a quantity of transmit antennas or a set of transmit antennas used during transmission of the CS frame; and the scheduling parameter comprises a burst period of sending the CS frame, a quantity of burst periods, a busy period of sending the CS frame within the burst period, and a time interval of sending the CS frame in the busy period receiving, by the CSI request apparatus, a channel state information response CRSP frame sent by a first CSI response apparatus, wherein the CRSP frame is a second public action frame, and comprises a first session parameter, the first CSI response apparatus is a CSI response apparatus that receives the first CREQ frame, the first session parameter is a group of session parameters that is of the at least one group of session parameters and that can be satisfied by a capability parameter of the first CSI response apparatus, and the CRSP frame is used to instruct the CSI request apparatus to receive, by using the first session parameter, a CS frame sent by the first CSI response apparatus; receiving, by the CSI request apparatus by using the first session parameter, the CS frame sent by the first CSI response apparatus; and measuring, by the CSI request apparatus, the CS frame to obtain CSI. sending, by a CSI request apparatus, a first channel state information request CREQ frame, wherein the first CREQ frame is a first public action frame, and comprises at least one group of session parameters that the CSI request apparatus expects to use, the first CREQ frame is used to request a CSI response apparatus that receives the first CREQ frame to determine, in the at least one group of session parameters, a group of session parameters used to transmit a channel state information sounding CS frame, and the CS frame is used by the CSI request apparatus to perform channel state measurement; wherein each group of session parameters of the at least one group of session parameters comprises a transmission parameter and a scheduling parameter; the transmission parameter comprises one or more parameters of a physical-layer protocol data unit, PPDU, format of the CS frame, or channel information, a transmission bandwidth, a modulation and coding scheme, or a quantity of transmit antennas or a set of transmit antennas used during transmission of the CS frame; and the scheduling parameter comprises a burst period of sending the CS frame, a quantity of burst periods, a busy period of sending the CS frame within the burst period, and a time interval of sending the CS frame in the busy period receiving, by the CSI request apparatus, a channel state information response CRSP frame sent by a first CSI response apparatus, wherein the CRSP frame is a second public action frame, and comprises a first session parameter, the first CSI response apparatus is a CSI response apparatus that receives the first CREQ frame, the first session parameter is a group of session parameters that is of the at least one group of session parameters and that can be satisfied by a capability parameter of the first CSI response apparatus, and the CRSP frame is used to instruct the CSI request apparatus to receive, by using the first session parameter, a CS frame sent by the first CSI response apparatus; receiving, by the CSI request apparatus by using the first session parameter, the CS frame sent by the first CSI response apparatus; and measuring, by the CSI request apparatus, the CS frame to obtain CSI.