The photochemical behavior of a photochromic liquid crystalline (LC) dendfimer of the second generation (G2) in chloroform and tetrabydrofuran was described．Thirty-six 4-n-hexyloxyazobenzene mesogenic fragments were attached in its periphery．The photochemical behavior of carhosilane dendrimer of the second generation (G2) was compared with that ofthe carbosilane dendrimer of the first generation (G1) and the mesogenic unit compound (M3). The quantum yield Ф and intensity of light absorption Ia of G2

G1 and M3 were determined． In chloroform and tetrabydrofuran (THF) Ф was in an order of M3>G1>G2

while

Is in chloroform and tetrabydrofuran (THF) had orders of G2>G1>M3 and M3>G1>G2

respectively．The reaction rate constant of the thermal back-isomerization kH at different temperature and the activation energy E of G2

G1and M3 were discussed．At the salnetemperature

kH in chlomfoform and tetrahydrofuran (THF) wasin an order of G1>G2>M3． The photoisomerization conversion percentage and trans/cis isomer absorbance ratio at the thermal back-isomerization of G2．G1 and M3 were described．The photoisomerization conversion percent were in chloroform and tetrahydrofuran (THF) showed orders of G1>M3>G2 and G2>G1>M3

respeetively．The trans/cis isomer absorbance ratio at the thermal back-isomerization A'／A'o in chloroform and tetrahydrofuran (THF) was in order of C2>G1>M3．