Lead is harmful heavy metal giving fatal damages to brain and nerve, and therefore, strict allowance standard has been adopted to industrial waste water(100 ppb), and to environmental and drink waters (10 ppb). A Pb(II) selective membrane filter was fabricated from the fibrous Ce(HPO₄)₂ H₂O (Cerium phosphate) crystal. Trace Pb(II) of ppb level was selectively captured on the membrane surface simply by filter the sample solution. Visual detection of ppb level of Pb(II) was realized by coupled with color development as PbS. The simple detecting technique can provide an on-site and low cost means of monitoring trace lead ion in environmental water and industrial waste water.