The effect of produced fertilizer (FV-01) from alkaline wastewater of agar production on the density, mass and yield of tea buds in Hanoi and Thai Nguyen was investigated on a narrow and extensive area. FV-01 from alkaline wastewater was tested on tea buds' density, mass and yield with different concentrations.Density, mass and yield of tea buds in Ba Vi, Hanoi and Dong Hy, Thai Nguyen for narrow area test with the concentration 1.35 litres/ha of FV-01 fertilizer were 1,443 (bud/m2), 94.8 (g), 10.9 (%) and 1,452 (bud/m2), 93.2 (g), 11.6 (%), respectively. Large area tests of tea buds showed that the concentration 2.7 liters/ha of the sprayed FV-01 fertilizer on yellow brown soil and yellow red soil increased 10.0 % and 11.2 % of the tea bud, respectively. These results proved that the concentrations in the range of 1.35 litres/ha -2.7 litres/ha of FV-01 fertilizer had higher density, mass and yield of tea buds, both the narrow area test and extensive area test than the control.