The invention discloses green silicate fluorescent powder with a narrow half peak width. The silicate fluorescent powder has a general chemical formula of (M1xBa2-x-u-k)(SiyM21-y)O4:uMn<2+>, kM3<2+>, wherein M1 is at least one of Sr, Ca, Mg and Cu, M2 is at least one of Ti, Zr, Ge and Sn, and M3 is one of Eu, Sm and Yb; x is greater than 0 and less than or equal to 0.2, y is greater than 0.8 and less than 1.0, u is greater than 0.05 and less than or equal to 0.15, and k is greater than 0 and less than or equal to 0.05. The invention also discloses a preparation method comprising: weighing raw materials and a fluxing agent, and performing mixing and grinding to obtain a mixture; performing high-temperature sintering on the mixture in a reducing atmosphere, and performing crushing, screening, alcohol washing and drying on the sintered mixture after cooling to obtain the narrow-half-peak wide-green silicate fluorescent powder. The preparation method of the fluorescent powder provided by the invention is simple and easy to control, needs a low sintering temperature during preparation, has a wide process window, and is suitable for large-scale industrial production; the obtained fluorescent powder has a narrow half peak width and a small particle size, is uniform in distribution, narrow in distribution range, good in chemical stability and strong in resistance to heat and humidity, and can be widely applied to LED illumination or display systems.