Transient discharging process of shallow electron traps in pulsed-laser deposited heteroepitaxial (Ba,Sr)TiO3 thin films has been recorded by Discharging Transient Spectrotroscopy.The results showed that there are two quasi-continuous shallow levels in heteroepitaxial (Ba,Sr)TiO3 thin films.One is introduced by bulk oxygen vacancies and the other by surface ones.The dominate electron traps in heteroepitaxial (Ba,Sr)TiO3 thin films are bulk oxygen vacancies.Energy level introduced by surface oxygen vacancies is slightly shallower than that by bulk ones for the absence of confined by upper semi-plene lattices.Capture cross section (σ =7.67 × 1 0-14 cm2),activation energy (Ea =0.309e V) and defect states density (N,≈ 4×1016cm-3) of bulk defects have been evaluated from the isothermal Discharging Transient Spectrum measured at various temperatures.