当代音韵学者在构拟中古音时多将果摄主元音构拟为ɑ,假摄为a,但通过对汉藏语言元音格局的比较,《广韵》歌戈麻三韵的异读纠缠,果假二摄的上古来源及后代音变,以及唐诗押韵情况的考察会发现为中古音设立ɑ、a对立并不可靠。而越南汉字音、朝鲜汉字音、日译汉音、汉藏对音、梵汉对音、侗台语的中古借词层显示果假二摄在中古主元音均应为a,其分别在于r介音的有无。而其他二等a类韵构拟也该重新思考。 Contemporary phonetic scholar in the formulation of the ancient Chinese when the vowels mostly as a pseudo-vowels, fake photo was a, but by comparing the pattern of Chinese-Tibetan vowel, “Guangyun” Gege three different rhyme entanglement, The origin of the fake two photographs and the sound changes of the posterity, as well as the investigation of the rhyming conditions of the Tang poetry, will find that the establishment of the middle-aged sound is not reliable. The Chinese loan words of Vietnamese, Korean Chinese, Japanese-Chinese, Sino-Tibetan pairs, Allegory of Sanskrit and Kamchatka indicate that the dominant vowel should be a, Does it have an audio? Other second-class a rhyme structure should also be re-thinking.