A method and an apparatus for determining transmit power are disclosed. The method includes: determining an E-DPDCH gain factor in compressed mode according to the number of E-DPDCH required for initial transmission of data; and determining transmit power of E-DPDCH according to the E-DPDCH gain factor in compressed mode. The E-DPDCH gain factor in compressed mode is determined according to the number of E-DPDCH required for initial transmission of data, and therefore, the E-DPDCH gain factor in compressed mode is determined accurately, the transmit power of E-DPDCH is determined accurately according to the E-DPDCH gain factor, the waste of transmit power of E-DPDCH is reduced, and therefore the system capacity is improved.