Objective To explore the effects of cyclic tensile strain (CTS) with varied intensity on glycosaminoglycan (GAG) synthesis of chondrocytes in primary cultured rabbits’ knees. Methods Articular cartilages of two knees in six New Zealand rabbits (at the age of one month) were obtained through aseptic surgery. Chondrocytes were resolved and isolated from articular cartilages by using 0.4% pronase and 0.025% Ⅱ collagenase. Then chondrocytes from the same rabbit were divided into three parts and inoculated separately on three BioFlex culture plates. After this, stimulation of cyclic tensile strain (sinusoidal wave, 0.3 Hz, 6 h/d)with different intensity (0%, 5% and 15%) was loaded to chondrocytes in monolayer cultured primary rabbits by means of a Flexercell 5 000 strain unit. The morphology of the cells was detected using inverted microscope at 24, 36, 48, and 60 hours of loaded CTS respectively. In the meanwhile, supernatants were drawn separately and GAG concentration was measured with Alcian blue precipitation. Finally, variance analysis of repeated measurement data was adopted to compare the variation of GAG concentrations in supernatants among CTS stimulation groups with different intensity. Results After cellular mechanical loading, it could be observed that chondrocytes exhibited a morphologic change from polygon to spindle shape, arranging perpendicularly along the radius of the cultured plates. Following the raising of strain intensity, GAG concentrations in supernatants were on the rise in proper order, with average concentration in each group being [(4.7±1.3), (6.3±1.1) and (8.0±1.8) ng/ml, F=15.970, P=0.000] respectively. Consistently, at the same time point, there were significant differences of GAG concentrations in supernatants among the three groups, with average concentration of 24 hour [(2.3±0.5) vs. (3.3±0.6) vs. (3.9±0.6) ng/ml, F=6.062, P=0.036], 36 hour [(4.0±0.7) vs. (4.6±0.8) vs. (6.8±0.2) ng/ml, F=16.720, P=0.004], 48 hour [(5.5±0.7) vs. (6.8±0.7) vs. (8.5±0.8) ng/ml, F=12.570, P=0.007], and 60 hour [(6.9±1.2) vs. (10.8±1.3) vs. (13.0±1.1) ng/ml, F=19.790, P=0.002] respectively. Meanwhile, there was a significant difference between two groups by using L-S-D method. In pace with the increase of total loading time, GAG concentrations in supernatants were gradually multiplied, concentration in each group being [0% CTS group (2.3±0.5) vs. (4.0±0.7) vs. (5.5±0.7) vs. (6.9±1.2) ng/ml, F=4.640, P=0.037], [5% CTS group (3.3±0.6) vs. (4.6±0.8) vs. (6.8±0.7) vs. (10.8±1.3) ng/ml, F=23.580, P=0.000], and [15% CTS group (3.9±0.6) vs. (6.8±0.2) vs. (8.5±0.8) vs. (13.0±1.1) ng/ml, F=9.638, P=0.005] separately. It could be stated that there exists an interaction between total loading time and loading intensity. This suggests that the longer, the total loading time, the bigger, the values of GAG concentrations in supernatants comparing with those in control group. Conclusion CTS may promote GAG synthesis of chondrocyte in primary monolayer cultured rabbits’ knees. The effects will increase along with the raising of strain intensity and duration. Key words: Chondrocytes; Cyclic tensile strain; Glycosaminoglycan; Rabbits; Articular cartilage