A simple and highly selective photometric determination of micro amount of tin is based on reverse phase chromatographic separation with TBP extrac- tion resin. More than twenty Kinds of mefials in minerals did not interfere. It molar absorptivity is 1.48 × 105 1 mol-1 cm-1 at 510 nm. The C. V. for sample containing 0. 019 % of Sn is 3.73% (n=15).The measurable concentration ran- ge is n × 10-3一10-1% of tin.