In order to optimize the melt spinning process of biodegradable as-spun linear aliphatic-aromatic co-polyester fibres, a fractional factorial experimental design and appropriate statistical analysis for the thirty-two screening trials involving five control parameters were used. Depending on previous studies (Younes and Fotheringham, 2011a, Younes, et al., 2009, 2010, Younes, et al., 2011b), the low melt flow index grade has been utilized in this work. Die head pressure of the extrusion machine, a range of crystallographic orders presented as full-width half-maximum of an X-ray scattering of as-spun fibres and thermographic measurement of extruded filament in the air quench cooling window were investigated. Statistical analyses explained the relationship between, on the one hand, throughput flow rate and spinning temperature of filaments and, on the other hand, the crystallographic structure of the as-spun filaments. It has been found that spinning temperature and metering pumps speed are by far the most important factors affecting the die head pressure. Low spinning temperature leads to higher viscosity, higher flow resistance through the spinneret's nozzle and high die head pressure. Crystallographic order is affected significantly by metering pump speed, and the interaction between spinning temperature and quench air cooling speed. Metering pump speed, spinning temperature, winding speed and quench air cooling speed affect the filaments' temperature average. The obtained optimization helps to produce the most satisfactory properties in the biodegradable fibre based textiles, as environmentally-friendly attractive materials alternative to commercial chemical fibres for different applications.