A　C18　monolithic　capillary　column　was　utilized　as　the　solid　phase　microextraction　column　to　construct　an　in-tube　SPME-HPLC　syslem　which　was　used　to　simultaneously　extract　and　delect　five　phonoxy　acid　herbicides,　including　2,4-dichlorophenoxyacetic　acid　(2.4-D),　2-(2-clUoro)-phenoxy　propionic　acid　(2,2-CPPA),　2-(3-chloro)-phenoxy　propionic　acid　(2,3-CPPA),　phenoxy　propionic　acid　(PPA)　mid　2-(2.4-dichlorophenoxy)　propionic　acid　(2,4-DP).　The　operating　parameters　of　the　in-tube　SPME-HPLC　system,　including　the　length　of　the　mono-lithic　column,　the　sampling　How　rate,　the　sampling　tune,　the?　elution　flow　rate　and　the　elution　time,　had　been　investigated　in　detail.　The　optimized　operating　parameters　of　the　in-tube　SPME-HPLC　system　were　as　follow;　the　length　of　the　monolithic　column　was　20　cm,　the　sampling　flow　rate　was　0.　04　mL/min.　sampling　time　was　13　min;　the　elution　flow　rale　was　0.　02　mL/min,　elution　time　was　5　min.　Under　the　optimized　conditions,　the　detection　limits　of　the　five　phenoxy　acid　herbicides　were　as　follows:9　μg/L　for　PPA,　4　μg/L　for　2,2-CPPA,　4　μg/L　for　2.3-CPPA,　5　μg/L　for　2,4-D,　5　μg/L　for　2,4-DP.　Compared　with　the　IiPLC　method　with　di-rect　injection,　the　combined　system　showed　a　good　enrichment　factors　to　the　analytcs.　The　re-coveries　of　the　five　phenoxy　acid　herbicides　were　between　79.　0%　and　98.　0%　(RSD≤3.　9%).　This　method　was　successfully　used　to　detect　the　five　phenoxy　acid　herbicides　in　water　samples　with　satisfactory　results.