<p>The hydrogen isotope composition of leaf wax <i>n</i>-alkanes (<i>δ</i>²H_alk) has been used to reconstruct hydroclimate conditions, yet the factors that influence it are not fully understood, particularly the control of soil pore water <i>δ</i>²H. This study monitored the temporal and vertical variations of peat pore water <i>δ</i>²H (<i>δ</i>²H_pw) from 2015 to 2019 in the Dajiuhu peatland, central China. Results showed that <i>δ</i>²H_pw was highly variable in the surface layers (0–10 cm; avg. −47 ‰, 1<i>σ</i> = 11 ‰) and remained almost constant in deeper depths (below 50 cm; avg. −56 ‰, 1<i>σ</i> = 2 ‰). The <i>δ</i>²H_pw of the 0–10 cm layer was strongly correlated with the preceding month’s precipitation <i>δ</i>²H (<i>δ</i>²H_p) in the adjacent area (<i>r</i> = 0.7, <i>p</i> &lt; 0.01), indicating that <i>δ</i>²H_p is the main factor affecting the temporal variations of <i>δ</i>²H_pw in the upper layers. Moreover, the surface (0–10 cm) peat pore water slightly deviated from the local meteoric water line, suggesting that evaporation may also have an effect on the <i>δ</i>²H_pw. These findings emphasize the importance of precipitation isotope composition in interpreting the <i>δ</i>²H_alk in peat deposits under subtropical climates.</p>