The ore-dressing tailing of bauxite (hereinafter referred to as tailing), one new kind waste of Chinese aluminium industry due to the application of ore-dressing-Bayer process and ore-dressing-sintering process in China, is rich in aliuminosilicate minerals such as kaolinite and thus meets the requirement of starting materials for geopolymer preparation.Geopolymer, derived from various waste but with excellent performance, is considered as the low-CO2 emissions and environmental cementitious materials.The inadequate long-term results, however,is severely harmful to its extensive application in practice, especially in construction.In this paper, the strength development of geopolymer mortars cured at ambient environment for 6 years is investigated.The geopolymerisition products and microstructure evolution are also studied using XRD, ESEM, TG-DSC and Mercury Intrusion Pore structure analysis (MIP).The results show that the strength of long-term mortars dose not reduce but steadily increases from 50.0MPa at early ages to 75.0MPa at the end of 6-year curing.The hardened samples become more compact with advancing age because of the continuous geopolymerisition reaction, which leads the porosity and the amount of large pores to reduce.The presence of prismatical crystalline phase, mainly composed of C, Ca, in the holes of long-term specimen implies the occurrence of carbonation of gels with atmospheric CO2.This carbonation is also confirmed by TG-DSC curves with an endothermic peak and weight loss of approximate 8.1% at 870 ℃.According to above observation, the geopolymer should be improved in the resistance to carbonation if it is used as binders in construction which is exposed to atmosphere or high CO2 condition.