Abstract: The object of this paper was to investigate the tensile properties of single fibers bamboo, Chinese fir, kenaf and ramie by a newly designed micro tension tester (SFI). The loaddeflection curve of single fiber testing showed that a linear behavior presented to failure. The average values of tensile strength of bamboo, Chinese fir, kenaf and ramie single fibers were 1 710, 1 258, 1 019, 1 001 MPa, respectively, and their tensile modulus were 27.1, 19.9, 30.8, 11.4 GPa, elongation were 7.0 %, 6.6 %, 3.2 %, 8.9 %, respectively. It showed that the mechanical properties of the four fibers were different. Among the fibers investigated, the bamboo fiber had the biggest tensile strength with the peak value reaching 2 708 MPa. The ramie fiber had the biggest fracture strain and the best flexibility but the smallest tensile strength and stiffness. The toughness of the kenaf fiber was the poorest but the elastic modulus value was significantly higher than others, its stiffness was the best. Bamboo fiber is the best from comprehensive mechanical properties.