A new surface engineering technology has been introduced that can dramatically change the morphology and composition of existing SnO2 nanorods (NRs) to SnOx nanobeads (NBs) + NRs with the addition of a 1–6s laser + convex lens pair (LCP) process. Unlike the existing flame chemical vapour deposition (FCVD) method, which has a two-dimensional effect on a sample, LCP can control a relatively local area with a radius of several microns, making it a more sophisticated and advanced process. Notably, the LCP process at each second was directly linked to the change in the composition of the surface of the SnO2 NRs, and the response to NO2 gas in the SnO2 NBs + NRs with 1second LCP process was improved by approximately three times compared to that of bare SnO2 NRs. Therefore, a new gas-sensing mechanism was proposed through comparing the types of oxygen defect on the SnO2 NRs surface during a slight morphological transition and thermodynamic data of the composition before and after gas sensing.