Barium gallium selenide （BaGa₄Se₇， BGSe） crystal is a novel infrared nonlinear optical material with excellent comprehensive properties. The current research priority lies in the preparation of large-size， high-quality BGSe crystals. The synthesis of high-purity BGSe polycrystalline raw materials over 500 g was achieved in a single batch using a two-temperature zone synthesis furnace. Subsequently， BGSe crystal boules with a diameter of ϕ60 mm were successfully grown via an modified Bridgman method. Through orientation， cutting， and polishing processes， laser frequency conversion devices measuring over 10 mm×10 mm×50 mm were fabricated. The prepared crystals and devices represent the largest dimensions reported to date， providing critical material and component support for mid- to long-wave infrared laser output.