Abstract: The poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) was dissolved by chloroform and N,N-dimethyl formamide (DMF) to prepare the spinning solution, and then P(3HB-co-4HB) nanofiber scaffold was fabricated by electrospinning. The P(3HB-co-4HB) nanofiber scaffold was coated with sodium alginate (SA) to obtain the P(3HB-co-4HB)@SA composite fiber membrane. SEM, specific surface area meter and atomic absorption spectroscopy were used to characterize fiber morphology, specific surface area, and residual ion concentration of P(3HB-co-4HB)@SA composite fiber membrane. The results show that when the spinning solution concentration is 12%, P(3HB-co-4HB) nanofibers exhibit a uniform morphology. With the static voltage increasing, the diameter of P(3HB-co-4HB) fiber decreases first and then increases. The P(3HB-co-4HB) scaffold material can increase the specific surface area of SA by 3.9 times. P(3HB-co-4HB)@SA composite fiber membrane has a maximum adsorption capacity of 26.25 mg/g and 36.25 mg/g for Cu²⁺ ions and Pb²⁺ ions, respectively, which is converted into SA adsorption capacity of 364.58 mg/g and 503.47 mg/g, respectively.