Abstract: This invention relates to a novel phosphate based green phosphor represented by the formula (Ln.sub.1-x-y Ce.sub.x Tb.sub.y) PO.sub.4 .multidot.wM where Ln refers to one or more than one of La, Gd, Y and M refers to one or more than one oxide of B.sub.2 O.sub.3, Al.sub.2 O.sub.3, In.sub.2 O.sub.3, ZrO.sub.2, Nb.sub.2 O.sub.5 and TiO.sub.2. Requisite materials are processed through blending, prefiring, firing and post-firing treatments to form the high performance phosphate based green phosphor. The processing steps of this invention effectively obviate the difficulties as associated with the prior technology, substantially improve the phosphor brightness, thermal stability, enlarge the specific surface of the phosphor, and reduce the phosphor consumption in screen coating, thereby reducing the picture tube manufacturing cost and eventually yielding the novel high performance phosphate based green phosphor.