Langley plot method and long-winded absolute method are used to calibrate sunphotometer. It is based on the obserbational data of sunphotometer obtained from the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) during the period from 1 September, 2006 to 31 August, 2007, homochronous surface conventional observation data, satellite data and radiosonde data. The results show that the error of scaling value may be large when selecting one eligible observation day. If the scaling value of several days in each band is averaged, the calibrate error between calculated and truth value will be still large. If the method of expected mean method and fitted mean method are screened, the scatter degree of daily scaling value will strikingly decrease and the standard deviation can be reduced by 70%~90%; After spots which deviate relatively distantly are deleted by using fitted mean method, the averge scaling value is close to the truth value.