The three series of PZN-based ceramics 0.75PZN-0.15BT-0.10PT、0.85PZN-0.10BT-0.05PT and 0.80PZN-0.20BT are prepared by the columbite method, and the effect of PbO deficiency in starting raw powders on the phase structure of calcined powders and ceramics sintered with Lead free atmosphere is investigated. At the same time, the effect of PbO deficiency on the dielectric properties is also studied. The results demonstrate that even minor content of PbO deficiency would result in pyrochlore phase in the calcined powders and sintered ceramics. With the increase of deficient PbO content, the perovskite phase content in both calcined powders and ceramics will decrease gradually. The dielectric constant of the three series of PZN-based ceramics is greatly increased with the increment of PbO deficiency, and their peak relative dielectric constant reaches the maximum value with 1% mole PbO deficiency. However, PbO deficiency hardly affected the dielectric loss of the PZN-based ceramics. The increase of dielectric constant results from the enlargement of the size of effective ordered micro-regions and the elimination of PbO film among crystal borders.