Bagasse lignin (BL) was extracted rapidly from bagasse with p-toluenesulfonic acid (p-TsOH) in one step. Using single factor test, the effects of extraction time, extraction temperature and p-TsOH mass fraction on the whiteness and yield of BL were investigated, respectively. Results show that BLwhiteness decreases with the increases of extraction time, extraction temperature and p-TsOH mass fraction. BL yield decreases with prolonging extraction time, while it increases first and then decreases with increasing extraction temperature and p-TsOH mass fraction. Using the method of response surface design, the extraction of light-colored BL was further optimized. Results show that 36.11% of BL whiteness and 9.59% of BL yield are obtained under the optimal extraction conditions of 15 min of reaction time, 80℃ of reaction temperature and 40% of p-TsOH mass fraction. Finally, the structure of BL was characterized by FTIR and 2D-HSQC NMR. The results show that BL is a typical GSH-type lignin, and the reductionsin contents of carbonyl and methoxyl in BL structure are beneficial to an increase in whiteness.