The atmospheric structure constant of refractive index C2n is an important parameter of denoting atmospheric turbulence. The C2n is measured both in noonday and at night in everyday at all seasons in Hefei, respectively, using QHTP-2 micro-thermal meter. The vertical profile of C2n in Hefei(0～25 km)is investigated by analysis of experimental data, and the statistical matrix and statistics distribution is discussed in detail. It’s shown that variance profile of C2n in Hefei coincide with lognormal distribution, the probability distribution of C2n has conspicuous difference day and night.