NiO, NiS and NiO–NiS nanocomposite thin films have been successfully fabricated by pulsed laser deposition. Their electrochemical properties are evaluated by galvanostsic cycling and cyclic voltammograms. Compared with NiO and NiS thin films, NiO–NiS nanocomposite thin film shows an improved electrochemical performance with a reversible specific capacity around 500mAhg−1 and good cyclability. Scanning electron microscopy, high-resolution transmission electron microscopy and selected area electron diffraction measurements are employed to study the electrochemical reaction mechanism of NiO–NiS nanocomposite electrode. These results reveal that NiO and NiS in the mixture films react with lithium separately and could be reversibly reproduced.