Strain-hardening cementitious composite (SHCC) is a kind of construction material that exhibits multiple cracking and strain-hardening behaviors. The partial replacement of cement with fly ash is beneficial to the formation of the tensile strain-hardening property of SHCC, the increase of environmental greenness, and the decrease of hydration heat, as well as the material cost. This study aimed to develop a sustainable construction material using a high dosage of fly ash (no less than 70% of the binder material by weight). Based on the micromechanics analysis and particle size distribution (PSD) optimization, six mixes with different fly ash to cement ratios (2.4–4.4) were designed. The mechanical properties of the developed high-volume fly ash SHCCs (HVFA-SHCCs) were investigated through tensile tests, compressive tests, and flexural tests. Test results showed that all specimens exhibited multiple cracking and strain-hardening behaviors under tension or bending, and the compressive strength of the designed mixes exceeded 30MPa at 28 days, which is suitable for structural applications. Fly ash proved to be beneficial in the improvement of tensile and flexural ductility, but an extremely high volume of fly ash can provide only limited improvement. The HVFA-SHCC mix FA3.2 (with fly ash to binder ratio of about 76% by weight) designed in this study is suggested for structural applications.