[ $Zn_{2(1-x)}Mn_xSiO_4$ ]$0.07{leq}x{leq}0.15$) green phosphor was prepared by solid state reaction. The first heating was at $900^{circ}C-1250^{circ}C$ in air for 3 hours and the second heating was at $900^{circ}C$ in $N_2/H_2$(95%/5%) for 2 hours. The size effect of $SiO_2$ in forming $Zn_2SiO_4$ was investigated. The temperature for obtaining single phase $Zn_2SiO_4$ was lowered from $1100^{circ}C$ to $1000^{circ}C$ by decreasing the $SiO_2$ particle size from micro size to submicro size. The effect of the activators for the Photoluminescence (PL) intensity of $Zn_2SiO_4:Mn^{2+}$ was also investigated. The PL intensity properties of the phosphors were investigated under vacuum ultraviolet excitation (147 nm). The emission spectrum peak was between 520 nm and 530 nm, which was involved in green emission area. $MnCl_2{cdot}4H_2O$, the activator source, was more effective in providing high emission intensity than $MnCO_3$. The optimum conditions for the best optical properties of $Zn_2SiO_4:Mn^{2+}$ were at x = 0.11 and $1100^{circ}C$. In these conditions, the phosphor particle shape was well dispersed spherical and its size was 200 nm.