In　this　work,　an　improved　approach　was　developed　for　the　construction　of　a　hydrofluoric　acid　etched　capillary　porous　joint,　and　the　pore　size　of　the　porous　joint　was　investigated.　Several　etching　factors　such　as　reagents　concentration　and　etching　temperature　were　optimized.　Results　showed　that　moderate　temperature　with　low　hydrofluoric　acid　concentration　was　helpful　for　proportional　etching.　Low-range　protein　molecular　weight　marker　labeled　with　acridinium　ester　was　used　as　pore-size　reference　for　pore-size　evaluation　of　the　joint.　A　homemade　CE　with　chemiluminescence　detection　system　was　used　for　the　analysis　of　the　acridinium　ester　labeled　protein　molecular　weight　marker,　and　the　results　showed　that　only　the　small　molecular　peptides　can　pass　through　the　etched　porous　joint　and　the　big　size　proteins　cannot.　The　penetration　of　protein　whose　molecular　mass　was　larger　than　6500　Da　was　a　signal　of　over-etching.　©　2009　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim.