;---------------------------------------------------------------- Soft X-ray solar irradiance (1991-2001) derived from Yohkoh/SXT. ;---------------------------------------------------------------- Aki Takeda, Loren Acton (Montana State University, USA) and Nicole Albanese (Tufts University, USA) Solar irradiance was calculated from the soft X-ray full-Sun images obtained with Soft X-ray Telescope(SXT) for the whole period of the Yohkoh mission (Sep-1991 though Dec-2001). The full-Sun integrated filter-ratio temperatures and emission measures are used to calculate isothermal solar spectrum, from which the soft X-ray flux included in the wavelength range 1-8A and 3-20A were derived in the unit of W/m^2. The derivation of SXT irraidiance is now mature due to the use of the most recent atomic database (CHIANTI ver. 8.07), and application of our latest calibration parameters on the stray light correction, updated CCD gain, and the newly introduced correction of SXT response on account of the deposit of some absorbing material on the SXT entrance filters during the first 14 months after the launch. While SXT's most reliable spectral range for irradiance is 3-20A, the irradiance for 1-8A was calculated for the comparison with GOES/XRS low-band flux(1-8A). The SXT irradiance is in excellent correlation with GOES/XRS flux, except the period around the solar minimum(1996) where the GOES flux mostly went under the instrumental detection limit. It turns out that SXT can provide more reliable values of the soft X-ray irradiance around the solar minimum.