Application of biochar in soil is being increasingly discussed as a mean to sequestrate carbon and improve chemical and physical properties for plant growth. Compared with the studies assessing the impact on water retention, little research has been published elucidating the mechanisms which were responsible for the change of water stable isotope extraction time. The impacts of biochar on water retention of three types soil (sandy, loam and clay) with different biochar application rates were investigated by extraction timing curve and mean proportional contribution. The mixtures were extracted by cryogenic vacuum distillation and analyzed with isotope ratio infrared spectroscopy. The results showed that the minimum extraction time (Tmin) was 30min for sandy soil, 45min for loam soil and 60min for clay soil. The biochar application rates changed the Tmin, as well as the water hydrogen isotope value and mean proportional contribution. The isotopic composition of extracted sandy soil water was more depleted in 2H with the increase of biochar application rates at Tmin, while the extent of deviation to the standard values displayed peak for loam and clay soil water hydrogen isotope. The results indicated that biochar application rate was directly correlated to the water retention of sandy soil, and it was increased with the increase in water retention of loam and clay soils, but not all biochar application rates had the same impact. The loam soil was more sensitive than the clay soil to the biochar application.