Through assessment of surface water quality at Siep stream in Di An city, Binh Duong province. Siep Stream is a level 1 tributary that flows into Dong Nai River. Dong Nai River is currently being exploited and used for domestic water supply purposes. Sampling location of Siep stream at the culvert on National Highway 1K from January 2022 to November 2023, through statistical monitoring data compared with QCVN 08-2023/BTNMT (level A) and QCVN 08: 2015/BTNMT (column A2) - National technical regulation on surface water, it shows that the parameters increase or decrease without stable, most tend to increase with about 86.9% COD exceeding the standard 1.0 ÷ 7.8 times, 95.6% SS parameters exceeding the standard 1.8 ÷ 30.4 times, 95.6% N-NH4 number exceeds the standard of 0.16 ÷ 21.8 times, 52.1% of N-NO2 parameters exceed the standard by 0.52 ÷ 8.9 times, 65.2% of P-PO4 parameters exceed the standard by 0.35 ÷ 6.25 times, 91, 3% of Colifrom parameters exceeded the standard of 1.0 ÷ 3.3 times. The WQI (water quality index) results show that the surface water quality of Siep stream is mostly average, this result is not suitable for domestic water supply purposes, there needs to be solutions to improve water quality at the area Siep Stream.