The terrestrial laser scanning (TLS) was employed to scan the vegetation in the eroded red soil region to measure the tree height and diameter at breast height, the projected leaf area index (PLAI) of forest canopy and understory was also obtained. The results showed that the PLAI value of vegetation in the study area was up to 0.60, while the PLAI value of forest canopy and understory canopy were 0.37 and 0.40, respectively. The variation coefficient of PLAI of the total vegetation was less than the value of forest canopy and understory canopy. The parent material is an important factor causing the difference of the vegetation structure varying from plots. The restoration of vegetation structure was in an order of phyllite rock > red sandstone > granite. The TLS based method could precisely measure the vegetation vertical structure with a precision higher than 80%, which suggests this method could be used widely in the eroded red soil region in southern China.