[Objectives] The winged pearl oyster (Pteria penguin) is one of the large marine economic molluscs that are used to produce mabé pearls. It relys on strong byssus to anchor itself to substrate and resist the impact of water flow and predators. The byssus secretion behavior and byssal properties are easily affected by the environmental factors. Therefore, this research aims to study the effect of salinity on byssus secretion and mechanical properties of P. penguin. [Methods] In this experiment, three different salinities (low salinity group of 30, control salinity group of 35, high salinity group of 40) were used to study the effects of different salinities on byssus secretion, diameter and breaking force of P. penguin. Mustcam USB digital microscope was used for measuring and recording the diameters of the proximal, middle and distal regions of newly secreted byssus to an accuracy of 0.01 mm. Tensile tester (HP-10, Handpi) was used for byssus breaking force determination without affecting the structural properties of the byssus. One-way ANOVA (LSD method) was used to analyze whether there were significant differences for the three byssus-related parameters among the three salinity groups. [Results] The results showed that there were no significant differences in the byssus attachment rates of P. penguin among different salinity groups (Fig. 2), but the total number of byssus secretion in the control salinity group (48.7 ± 15.1) was significantly higher than that in the low salinity group (24.7 ± 5.0) and the high salinity group (13.3 ± 1.5) throughout the whole experimental period of 72 h. During the first 6 h of the experiment, the byssus first attachment rate in the control salinity group was significantly higher than that in the low salinity and high salinity groups (P < 0.05), but no significant difference was identified in the following hours (12 h, 18 h, 30 h, 42 h, 54 h and 66 h) in the byssus first attachment rate in the three salinity groups (Fig. 3). The measurement results of byssus diameter showed that the distal diameter of byssus was significantly different from the middle or proximal diameter (P < 0.05) under the same salinity. Therefore, when investigating the effect of salinity on the diameter of byssus, the whole byssus was still divided into three parts. There was no significant difference in the diameter of the same part (proximal, middle and distal diameter) of the byssus under 3 different salinities (Fig. 4), while salinity had significant effects on the byssus breaking force (Fig. 5), and the byssus breaking force in the control salinity group was significantly higher than that in the low salinity and high salinity groups (P < 0.05). [Conclusion] The above results show that in high salinity of 40 or low salinity of 30, byssus secretion is inhibited in the initial stage, probably due to the need to close the shell and reduce energy consumption to adapt to the environment. There is no significant difference in the first attachment rate among the three salinity groups. Salinity significantly affects the byssus re-attachment rate and breaking force, but not the byssus diameter. This study would provide valuable information for P. penguin culture and nucleus-inserting and pearl production.