While brown carbon (BrC) might play a substantially important role in radiative forcing, an estimation of its light absorption contribution with high-time resolution is still challenging. In this study, a multi-wavelength (370–950 nm) Aethalometer was applied to obtain the wavelength dependent light absorption coefficient (σabs) of aerosols, before and after heated to 250°C. An improved absorption Ångström exponent (AAE) based method was developed to evaluate the contribution of BrC to light absorption at the wavelength of 370 nm (σabs,BrC/σabs,370nm). The σabs,BC at the wavelength of 370 nm was determined from the field measured AAE over the wavelength of 880–950 nm with one-hour resolution. The simultaneous measurements of heated aerosols help confirm the negligible influence of BrC on the σabs over 880–950 nm. Meanwhile, σabs,BrC/σabs,370nm was also estimated by the previously reported methods by assuming AAE to be one (Method I) and based on the light absorption enhancement (Method II). While the estimated σabs,BrC/σabs,370nm based on our developed method and Method I is highly correlated (r2 = 0.78), the difference could be as large as > 20% on average. The mean σabs,BrC/σabs,370nm was obtained to be negative with Method II, indicative of net production of BrC when the aerosols were heated. The difference of the σabs,BrC/σabs,370nm obtained by our developed method and Method II was ~40% on average and much higher (> 50%) during noon hours, when secondary organic aerosols and sulfate were abundant. We propose that it is more suitable to use AAE around 0.7 for “pure” BC to evaluate the contribution of BrC to light absorption in the PRD region. The developed method would help improve the understanding on the light absorption and climate forcing of BrC.