Fly ash-based cordierite ceramics samples were prepared with fly ash, talc, alumina and magnesium oxide, by adding yttrium fluoride (YF3) with mass fraction of 0%, 0.5% and 1.0%, respectively. The effect of YF3 on phase composition, microstructure and physical properties of samples were studied. The results show that the introduction of YF3 reduces formation temperature of cordierite, improves phase conversion rate of cordierite, significantly increases the mechanical properties and has a moderate positive effect on thermal properties of samples. When the YF3 content is 0.5%, the performance of sample is the best. For the sample with 0.5% YF3 content, when the sintering temperature is 1 300 ℃, no obvious peak corresponding to any impurity is found in XRD patterns, the bulk density of sample is 2.15 g·cm-3, the open porosity is 7.49%, the water absorption is 3.49% and the compressive strength is 252.27 MPa. After 5 times heat shock experiments, the compressive strength is still high to 204.65 MPa. The heat capacity is 0.770~0.931 J/(g·℃) (25~150 ℃), and thermal expansion coefficient is 2.54×10-6℃-1 (100~800 ℃). The bulk density of sample with 0.5% YF3 content increases by 5.2%, open porosity decreases by 58.6%, water absorption decreases by 60.6%, compressive strength increases by 4.6 times, heat capacity increases and the thermal expansion coefficient decreases, compared with the sample without additives. In the sintering process of fly ash-based cordierite ceramics, the introduction of YF3 can form a liquid phase at a lower temperature, improve the mobility of elements, and promote the development of grains and fine grain size. As an effective sintering additive, YF3 significantly improves the comprehensive properties of fly ash-based cordierite ceramics with a small content. This work broadens the additives range for high quality ceramic materials, which provides reference for excellent materials sintered at high temperature.