A transmit power control method and system used in radio communications between a transmitting station and a receiving station is provided. The method and system employ a so-called double closed-loop control technique, and target signal quality is updated so that data quality received at the receiving station satisfies prescribed target data quality. When data are transmitted discontinuously, first target signal quality updated immediately before an idle period is held, and second target signal quality higher than the first target signal quality is set when data transmission resumes immediately after the idle period. The transmit power of the transmitting station is regulated so that signal quality at the receiving station satisfies the second target signal quality when the data transmission resumes.