The present invention provides a method for determining the number of random access channels which is applied to a time division duplex system. The method comprises: a terminal determining configuration parameters related to the number of the random access channels in an UpPTS based on system configuration, said configuration parameters including the number of downlink-to-uplink switch-points in one radio frame NSP, the density of PRACHs in a random access configuration DRA, a system frame number of a system frame in which said UpPTS is located nf, and a version index corresponding to a PRACH configuration index rRA; and said terminal then calculating directly the number of the PRACHs in said UpPTS based on the configuration parameters. The present invention also provides a method for sending a SRS of a time division duplex system using the method for determining the number of the random access channels.