To explore the mechanism of the influence of calcium dissolution on the micro properties of self-compacting recycled concrete (SCRC), considering the effects of the replacement rate of recycled coarse aggregate (RCA) and the dosage of fly ash (FA), an experimental study was conducted on the micro properties of SCRC under accelerated calcium dissolution conditions using ammonium chloride solution. The experimental results show that as the dissolution age increases, the ultrasonic velocity of SCRC decreases, and the proportion of most probable and large capillary pores increases. The porosity of ordinary SCRC continues to increase, while the porosity of SCRC mixed with FA first decreases and then increases. Within the same dissolution age, as the replacement rate of RCA increases, the ultrasonic velocity of SCRC, and the internal pH value and size of the dissolution transition zone decrease; With the increase of FA content, the ultrasonic velocity of SCRC first increases and then decreases, and the internal pH value and the size of the dissolution transition zone increase. During the dissolution process, when the FA content is 10% or 20%, the pore structure of SCRC is refined and its resistance to dissolution is improved. However, when the FA content is 30%, the pore structure of SCRC deteriorates and its resistance to dissolution decreases.