Size-tunable polyaniline nanotubes (PANI NTs) were fabricated by in-situ polymerization of aniline on an electrospun polystyrene (PS) surface. The morphology and electrochemical properties of the PANI NTs were governed by the size of the PS fiber, which is demonstrated by scanning electron microscopy (SEM) and cyclic voltammetry (CV). The coordination interaction of PANI NTs with Pb(II) ions was studied by ultraviolet-visible-near-infrared (UV-Vis-NIR) spectroscopy. Results showed that the PANI NT-modified glassy carbon electrode (PANI NT/GCE) exhibited high voltammetric response to Pb(II) ions by square wave anodic stripping voltammetry (SWASV), and the sensitivity to Pb(II) determination was strongly related to the diameter of PANI NTs. The design of orthogonal experiment was done to obtain optimal experiment condition. Under such optimal condition, a sensitivity of 0.2 mu A nM(-1) to Pb(II) ions determination was achieved at the PANI NT/GCEs with the PANI NT diameter of 400 nm in a coating amount of 3.54 mu g cm(-2). The PANI NT/GCEs also showed a good response to Cd(II) ions. The limits of detection were found to be 9.65 x 10(-11) mol L-1 and 2.67 x 10(-10) mol L-1 (S/N > 3) for the individual detection of Pb(II) and Cd(II) ions, respectively. The PANI NT/GCEs were successfully applied to simultaneously determine Pb(II) and Cd(II) ions in water samples with good reproducibility and stability. (c) 2018 Elsevier Ltd. All rights reserved.