Abstract: This paper studied the pholocrosslinking reaction of sensitized and unsensilized 3,4-polyisoprene-2,6-bis(4'-azidobenzal)cyclohexanoncIt was found that in the system of sensitized 3,4-polyisoprenc-2,6-bis(4'-azidobenzal)cyclohexanonc,the number of double bonds decreased greatly and the content of nitrogen increased 4 to 5 times than unsensitized system.By means of IRand LCfor measurement of the photocrosslinking products and its CC1₄ extractives respectively,it was confirmed that the essential reaction in benzophenone-scnsitizcd system was the addition between dinitrene and the external double bonds which were activated by benzophenonc,although the cyclized reaction was the principal mode of external bonds consume.