The photoisomerization behavior of benzylidene-acetophenones, known as chalcones, was studied. We synthesized the chalcone derivatives that have ether groups at 4 and 4' positions. Due to the electron donating ability of the ether oxygen, the bond order of the single bond between two phenyl ring of the chalcone strengthened, which eventually increased the rotational barrier of the single bond. The rotational barrier of the single bond is about 20-22 kcal/mole. Photo-irradiation with the 365nm light monotonously decreases the 340nm peak. However, the photo-irradiation with 254nm light induce two competing processes and produced rather complicated absorption profile.