An investigation was made of how the conditions of formation affect the porous structure, sorption properties and strength properties of nanocomposite sodium alginate fibres. It was found that the sorption properties of these fibres are determined by the hydrophilic nature of the material. The strength properties, given low deformability at the stretching stage, depend mainly on the value of the as-spun draw ratio. In SEM+EDS testing the presence of the natural hydroxyapatite (HAp) or $SiO_2$ nanoadditives which had been added to the fibres was detected.