By data mining in works of Jahiz, i.e. the Arabic proficient author and scientist in 3rd Hegira century (10th AD cen.), we may find that on most of occasions, he has referred to Iranian culture and civilization. Efforts made by Jahiz concerning to Iranian culture and civilization are to the extent that make him to leave his Arabic dogm and to acknowledge to Iranian deserving position among civilized nations of the world at that time and to introduced it as one of four noteworthy nations in the world at the given period. By pondering on two books of Al- Mahasen Val-Azdad and At-Taj Fi- Akhlagh Al-Molouk which attributed to Jahiz, we find that Iranian feasts like Norouz (NewYear holiday on March), Mehregan (Ahuraic festival on October) and Fassad (Pitcher- Throw away feast on June) with all of their customs and rites were held during Abbasid Caliphate with a lot of mirth and splendor and Abbasid kings welcomed such feasts in order to increase their revenue by receiving gifts granted in these festivals