Ultraviolet total ozone unit (TOU) is one of the main payloads on FY-3A meteorological satellite and the first instrument for daily global coverage of total ozone monitoring is independently designed and manufactured by China. It has been in-orbit for almost seven years from May 2008 to March 2015. The preliminary study shows that the radiation response FY-3A/TOU instrument is different for different spectrum bands ［the response of the instrument with radiance larger than 6.6 μW/(cm2·nm·sr) is obviously different from the instrument with radiance less than 6.6 μW/(cm2·nm·sr)］. It has the problem of bilinear response. A method is introduced for ultraviolet band in-orbit cross-calibration based on the data detected by global ozone monitoring experiment 2 (GOME-2) on European Metop-B satellite. The data of FY-3A/TOU L1B are checked by in-orbit cross-calibration, and then the rea-time comparisons and corrections of instruments′ detection values are made. The calibration results chosen from February 2013 to February 2015 indicate that the comparison slopes of radiation are all very close to 1 before August 2013, which mean that the detected radiance of TOU is fairly accurate. However, the slopes become a little larger after August 2013, the detected radiance of TOU is relatively larger than GOME-2, which means that the detected response FY-3A/TOU is changed. Although the equation slopes are variant, the relation coefficient between TOU and GOME-2 keeps better linear dependence (R2＞0.96). It means that the later measurements of TOU can be corrected by use of cross-calibration equation.