To distinguish the effect of gradeⅡfly ash from different power plants on the performance of long-age mortar, we used four kinds of commonly used fly ash in Guizhou region (from Yaxi, Dafang, Liupanshui and Douyun) to explore the influence of different fly ash on the mechanical properties, porosity, water absorption and microstructure of long-age mortar. The results show that the flexural strength and compressive strength of long-age mortar improved by 94.6% and 52.1% (Yaxi), 71.6% and 49.5% (Dafang), 100.0% and 92.0% (Liupanshui) and 51.8% and 47.6% (Douyun) respectively, after the replacement of cement with fly ash of equal amount from those regions. The greater the content of fly ash, the greater the increase of the flexural strength and compressive strength of mortar, and the greater the decrease of porosity, which was 29.7%(Liupanshui), 40.0%(Yaxi), 28.7%(Duyun) and 34.9%(Dafang), respectively. Maximum water absorption of these four kinds of fly ash mortar reduced by 21.6%（Liupanshui）, 44.0%(Douyun), 39.8%（Yaxi）和38.9%（Dafang）, respectively. Comprehensive analysis found that, after curing for 1 000 days, fly ash was still active in the mortar performing filling and pozzolanic effect, among which that with lower activity mostly had a filling effect on the porosity of mortar.