Demersal and semi-demersal fishes were the important species which contributed a relatively high ration in the total marine catches. Research on standing stock omass of fishes are now considered as an urgent need to give advices for fisheries planning management and sustainable use of the marine resources. However, the accuracy and precise estimate have limitations and need to be improved. There are a number of methods used to estimate the stock size of fishes, swept-area method using bottom trawlnet is one of the most popular approaches used in the world. This paper reviews the use of this method in estimation of fish stock size in Vietnam.