Tree mortality induced by drought and warming is related to the dysfunction in hydraulic traits that regulate the process of water transport. Xylogenesis, the sequential phases of cell production, enlargement and wall deposition, influences tracheid size and biomass accumulation in wood, thereby modulating xylem hydraulic traits. Nevertheless, the specific impacts of xylogenesis dynamics on xylem hydraulic traits in trees remain less well understood. Here, we monitored the xylogenesis of Pinus tabulaeformis at two semi-arid sites, representing the northern and southern extremes of its range on the Loess Plateau in 2018. We measured anatomical traits of the corresponding 2000 tracheids and assessed the relative contributions of cell enlargement and wall deposition to xylem hydraulic efficiency (theoretical hydraulic conductivity) and hydraulic safety (conduit wall reinforcement). Cell enlargement spanned from late-March to late-October, while secondary wall deposition lasted from early-April to early-November. A bimodal growth pattern was detected at the northern site, resulting in an intraannual density fluctuation in the tree ring. Theoretical hydraulic conductivity regularly decreased along the tree rings, whereas conduit wall reinforcement was close to zero before 30 % of the tree ring and then increased in fluctuation. Structural equation models demonstrated that the duration of cell enlargement affected the theoretical hydraulic conductivity and conduit wall reinforcement via its effect on tracheid radial diameter, while the effect of wall deposition was marginal. The intra-annual density fluctuations did not significantly impact xylem hydraulic traits, likely due to the marginal changes in tracheid radial diameter along the tree ring. Our findings suggest that water deficits occurring during the early growing season could potentially constrain cell enlargement, thereby reducing the hydraulic efficiency but potentially increasing the resistance of xylem to the embolism in pine.