Abstract: The improved cross-correlation algorithm for the strain demodulation of Vernier-effect-based optical fiber sensor (VE-OFS) is proposed in this article. The algorithm identifies the most similar spectrum to the measured one from the database of the collected spectra by employing the cross-correlation operation, subsequently deriving the predicted value via weighted calculation. As the algorithm uses the complete information in the measured raw spectrum, more accurate results and larger measurement range can be obtained. Additionally, the improved cross-correlation algorithm also has the potential to improve the measurement speed compared to current standards due to the possibility for the collection using low sampling rate. This work presents an important algorithm towards a simpler, faster way to improve the demodulation performance of VE-OFS.