The physical properties of air-jet texturing yarn with various processing conditions are investigated in this paper. Physical and mechanical properties of air-jet textured yams manufactured with Hemma Jet T311 type are measured with various processing conditions such as overfeed, air pressure and dry/wet effect. Polyester filaments used are 75d/36f semi dull, which is used for core, and 75d/72f semi dull, which is used for effect in the yarn, respectively. The other polyester filaments used are 40d/24f, which is high shrinkable yam and 50d/24f, which is cation fibre, both are used for core in the yam. Physical properties measured are yarn linear density, yarn stability(instability and decay) by the stress-strain dlayim, loop structure by SEM. Mechanical properties measured are tenacity, modulus, ym, compression, and bending property. These physical and mechanical properties are analysed and discussed with various processing parameters such as overfeed, air pressure and dry/wet condition.