Thallium (Tl) is a dispersed element and it seldom occurs in the form of independent minerals. So the element is hard to form any independent deposit. The world annual production of Tl is about 13 ton, most of which is recovered as by|product from non|ferrous metal metallurgical products. Reported in this paper is the only large|sized independent Tl deposit in the world, of which the Tl ores can be mined, ore|dressed and smelted independently. Bio|enrichment and hydrothermal reworking are the two important metallogenic mechanisms of this Tl deposit. This paper will give a discussion to the Lanmuchang Tl deposit in the following respects including its geological characteristics, element association of Tl, Hg, As and Au and W, sulfur isotopic composition, involvement of hallogens in metallogenesis and the metallogenic models. Tha theium (Tl) is a dispersed element and it seldom occurs in the form of independent minerals. So the element is hard to form any independent deposit. The world annual production of Tl is about 13 ton, most of which is recovered as by product from non | ferrous metal metallurgical products. Reported in this paper is the only large | sized independent Tl deposit in the world, of which the Tl ores can be mined, ore | dressed and smelted independently. Bio | enrichment and hydrothermal reworking are the two important metallogenic mechanisms of this Tl deposit. This paper will give a discussion to the Lanmuchang Tl deposit in the following respects including its geological characteristics, element association of Tl, Hg, As and Au and W , sulfur isotopic composition, involvement of hallogens in metallogenesis and the metallogenic models.