The effect of soil relative water content (SRWC) and air relative humidity (RH) on pupal development, survival, and water-loss dynamics in Bactrocera tau (Walker) were evaluated under experimental conditions. In soils with SRWC of 0, 20, 40, 60, 80 and 100%, most of the mature larvae (75.83%) selected soil sites with a SRWC of 20–60% to pupate. When SRWC was 40 and 60%, pupae had the shortest pupal duration (7.54 and 7.65 d) and the highest eclosion rate (83.58 and 90.53%), whereas when it reached 100%, all pupae failed to survive. In air of RH 0, 52, 76 and 100%, pupal cumulative water loss increased with increase of the treatment time, and reached up to 63.52% for RH 0%, 45.42% for RH 52%, 34.23% for RH 76% and 10.99 for RH 100% at the last day before eclosion. Cuticular permeability attained to 9.95, 5.90, 3.67 and 0.72 μg/(cm² · h · mmHg) in the first day of pupal life, respectively, and then declined by 36.01, 21.30, 13.26 and 2.63% in the second day. In air at RH 100%, the shortest duration (8.07 d) and the highest survival rate (90.55%) of pupae were attained, while only a few (3.03%) could survive at RH 0%. These results imply that high SRWC and low air RH were unfit for the development and survival of B. tau pupae.