A sulfate dry-wet cycle test was conducted on ultra-high performance concrete (UHPC) mixed with recycled sand and ultra-fine fly ash, in order to investigate the sulfate resistance of recycled sand UHPC. The compressive strength, relative dynamic elastic modulus and mass change of specimens before and after sulfate solution corrosion were tested. The effect of compounding recycled sand and ultra-fine fly ash on sulfate ion transport was analyzed by ion titration to determine the distribution of sulfate ions at different corrosion depths. The results show that the corrosion resistance coefficient of UHPC increases first and then decreases with the increase of ultra-fine fly ash content after 90 sulfate dry-wet cycles. When the content of ultra-fine fly ash is 20% (mass fraction, the same below), the corrosion resistance coefficient and relative dynamic elastic modulus of whole corrosion process are the largest, and the sulfate ion content is low. At 50% of recycled sand, UHPC has the highest relative dynamic elastic modulus before 45 dry-wet cycles, and the lowest sulfate ion content at the same depth. The UHPC compounded with 20% ultra-fine fly ash and 50% recycled sand has the best sulfate resistance.