This study has focused on relation between the sintering condition and microwave dielectric properties for YAG ceramics. Both dielectric constant (epsilon(r)) and quality factor (Q . f) of the prepared samples were increased with increasing sintering temperature from 1400 to 1650 degrees C, suggesting that the densification is closely related to the epsilon(r) and the Q . f. The epsilon(r) was independent of the grain growth resulting from longer sintering duration time at 1650 degrees C because of no difference in the volume fraction of pores. On the other hand, the Q . f was responsible for the grain growth, indicating that the decrease of the grain boundary resulting in higher Q . f. The Q . f value of the sample sintered at 1650 degrees C for 24 hrs reveals 440000 GHz, which is approximately a half, compared to that of the single crystal.