A Simple and an efficient procedure for the synthesis of 2-cinnamoyl-benzo[g] indazoles are reported. A new series of 2-cinnamoyl- benzo[g] indazole derivatives were synthesized by the treatment of appropriate of 2-(Substitued arylidene)-1-tetralones with cinnamoyl hydrazide using catalytic amount of acetic acid in polyethylene glycol-400 as reaction solvent under mild reaction condition. The newly synthesized compounds were characterized by the spectral analysis. The advantage of this method is simple and efficient work up, shorter reaction time and use of inexpensive catalyst is reported.