Abstract Exploring the influence of environmental factors on the distribution and Growth on Cladophora spp., Microspora spp. and Rhizoclonium spp. at Nan River were carried out from 3 sampling sites during November 2015 to March 2016, the samples were collected by monthly. The results showed that the high abundance of macroalgae were found during January to March 2016. The most distribution of algae can be found at site NongBao was Cladophora spp. 64-80% of square meter area. The physico-chemical parameters were recorded that related to algae growth in this study were air temperature 25.0 – 34.0 °C, water temperature23.5 – 28.5 °C, water depth0.2 – 0.8 m., velocity0.33 – 0.80 ms-1, turbidity10 – 33 NTU, pH7.90 – 8.21, DO 7.0 – 8.8 mgL-1, BOD0.4 – 2.0 mgL-1, conductivity226.2 – 272.8 μscm-1, TDS225.1 – 245.5 mgL-1, NO3 --N0.1 – 0.7 mgL-1, NH4 +-N 0.12 – 0.23 mgL-1and orthophosphate 0.01 – 0.18 mgL-1. The most factor that influenced the distribution of diatoms and macroalgae was the physical factors such as water velocity and turbiditymore than Chemical factor as DO, BOD and Nutrients.