Abstract: In order to investigate the size effect and the sensibility of strain rate of the jute yarns,the quasi-static tests were conducted by utilizing a C43 electromechanical universal test system and dynamic tests were performed by utilizing a CEAST 9340 drop-weight impact system.The correlations between mechanical parameters (Young's modulus,tensile strength,ultimate strain and toughness) and experimental conditions (gauge lengths and strain rates) were obtained through the tests.The samples with six different gauge lengths (25,50,100,150,200 and 300 mm) were tested at the strain rate of 1/600 s^-1 in the quasi-static tests,and the samples with the gauge length of 25 mm were tested over four different strain rates (40,80,120 and 160 s^-1) in the dynamic tests in which the strain rate was a variable.The experimental results show that Young's modulus increases initially,and then tends to be stable when the gauge length is larger than 100 mm,while tensile strength,ultimate strain and toughness decrease with increasing the gauge length.As the strain rate increases,Young's modulus and tensile strength increase,while ultimate strain decreases initially and then maintains constant,and toughness decreases initially but then increases.Due to the large scatter in the material properties of plant yarns,Weibull distribution was used to fit the experimental data,by which the distribution of tensile strength of the jute yarns under different experimental conditions (gauge length and strain rate) were obtained.