The photochemical behavior of a photochromic carbosilane liquid crystalline(LC) dendrimer of second generation (G2) in chloroform and tetrahydmfuran were described．Thirty-six 4-hexyloxyazobeazene mesogenic fragments were attached in its periphery．The maximum absorption wave length and molar extinction coefficient of G2 were determined．The reaction rate constants of trans/cis photochemical isomerization and positive/counter photochemical back-isomerization and the equilibrium constant of photochemical back-isomerization reaction for G2．G1 and M3 were discussed．Their absarbance A360 in CHCl3 and maximum absorption wave length λmax in CHCl3 and THF around 360 nm arc in G2>G1>M3 and G2max of G2 in solutions shows an order of DMF>C6H6>CHCl3>THF>EtOH．Their molar extrinction coefficient ε360 in CHCl3 and THF and their reaction ratio constant of photochemical isomerization kp in CHCl3 are in G2>G1>M3 and G2-1s-1

but that of the photochromic LC polysiloxanes containing the azobenzene moieties is 10-8s-1

thus the phomresponsive rate of the LC pbotoehromic dendfimer G2 is 107 timeslarger than that of the latter．