Early age cracking has been an ever-present problem during the application of recycling coarse aggregate concrete.Influences of recycling coarse aggregate size( 5 ~ 15mm,15 ~ 25mm and 25 ~ 31.5mm) on early age( age: 0 ~ 24h) cracking tendency of recycling coarse aggregate concrete( RC) and recycling coarse aggregate concrete with fly ash( FRC) were studied based on slab test method.The results of the early age cracking indexes and cracking processes indicate that the large aggregate size( 25 ~ 31.5mm) corresponds to the decrease of cracking damage for recycling coarse aggregate concrete targets,the slab test samples with 15-25mm of recycling coarse aggregate size has the optimum efficiency in terms of anti-cracking ability when comparing to the other two kinds of FRC samples for RC samples with 15% fly ash.The experimental result in this paper is very beneficial to the optimization and design of recycling coarse aggregate concrete on anti-cracking mix proportions.