This article, at first, reviews the tone scheme theories of seven-character poems in Ming and Ching Dynasties and then investigates the tone patterns of more than one thousand poems by Tang poets. The tone pattern of seven-character poems by Tang poets can be divided into two types: the so-called multiple rhyme-word seven-character poems, and one rhyme-word seven-character poems. The so-called multiple rhyme-word seven-character poems follow the regulation whose tone scheme is very similar to that of regulated poems, and the tone scheme of the one rhyme-word seven-character poems is, on the other hand, very similar to that of the old style poems. Lastly, this paper finds that the Tang poets may not strictly abide by the fore-mentioned regulation. Where there is a leeway in between, poets would write freely in terms of tone scheme