Concrete specimens were stored in dry environment(21℃ and the relative humidity is 37%) after being normally cured for 3， 7， 28d(SC3, SC7 and SC28), respectively. Mechanical properties, frost resistance and chloride penetration resistance were tested at different ages. Furthermore, the elastic wave velocity was employed to quantitatively characterize the levels of drying initial defects and microstructural analyses were also carried out to reveal the generating mechanism of the drying initial defects. Results show that the 90d compressive strength/splitting tensile strength of SC3 and SC7 series decrease by 11%/13%， 7%/6% as compared to that of SC28, respectively, although the 28d compressive strength/splitting tensile strength of SC3 and SC7 are not significantly different from those of SC28. The frost resistance and chloride ion permeability resistance of SC3/SC7 are significantly lower than those of SC28. Microstructural analyses revealed that drying initial defects in concrete are related to the microstructure of hydration products, content of harmful pores and microcrack density in the mortar matrix affected by drying.