The 150 MeV linac of Taiwan Photon Source was commissioned in June 2011. It consists of 90 keV electron source, bunching system and three S-band accelerating sections driven by three high-power klystrons. The rf system is equipped with rescue option such that the rf power from second klystron can be split and fed into both accelerating section-1 and -2. The rescue operation will be needed in the event of a failure occurred at the first klystron. In this report, the rescue capability will be illustrated and the test results will also be discussed.