It has been shown that the photoinduced liquid crystal (LC) alignment is inferior to the rubbing-induced alignment, which requires the optimal UV exposure conditions for improvement of photoalignment. For a cinnamate-branched polymer, we have investigated the effects of various LPUV exposure parameters on the photoinduced LC alignment over it. The uniform photoalignment with good thermal stability has been induced by LPUV irradiation with much more (about 10 times) exposure energy than that generating the maximum anisotropy of the photoalignment layer, employing both a polarizer with a higher extinction ratio and an optical filter to cut off deep UV.