Abstract: Six timber short columns were reinforced by wrapping different layers of single or hybrid CFRP and AFRP sheets of which a column without any knags and one with knags were picked as contrast specimens． The axial compressive behavior of the columns was analyzed，including the ultimate carrying capacity，the load-deformation and load-strain curves． It was also observed the shape features of the faiure section． The test results show that the axial compressive ultimate bearing capacity and stiffness of the short columns are decreased by about 23% and 60% due to the existence of knags，which are improved obviously afte reinforcing the columns by FＲP sheets． The comparison of the load-strain curve shows that the transverse strain near the knag is much higher than that far from the knag．Radial cracks were found on the failure section and fibers near the cracks are compressed to yield．