Sardines are key species, which contributes about 25% total biomass of small pelagic fishes, recognized as highly commercial importance in Tonkin Gulf. This study applied general additive models (GAMs) to explore the relationship between abundance of sardines and four dynamic environmental factors (temperature, surface height anomaly, chlorophyll a, current) and a static variable ‘depth’ in Tonkin Gulf. Data on abundance of sardines were collected during three acoustic surveys in 2012 and 2017, incorporated with satellite derived environmental data sets. Results indicated that abundance of sardines quite related to several key environmental factors (temperature, chlorophyll a, current); and also associated with bathymetry. GAM models were able to explain about 52.5-77.9% for the distribution of sardines in Tonkin Gulf.