Polycarboxylate　superplasticizer　(PCE)　was　usually　sensitive　to　clay　in　mortar　or　concrete.　The　flow　properties　of　cement　pastes　and　mortars　for　PCEs　with　either　kaolin　or　bentonite　were　studied　systematically.　The　results　showed　that　bentonite　had　a　stronger　influence　on　PCE＇s　performance　than　kaolin,　even　no　fluidity　when　bentonite　dosage　was　more　than　2%.　The　adsorption　amount　of　bentonite　on　PCE　was　about　5-10　times　more　than　that　of　kaolin,　and　PCE＇s　adsorption　on　clay　was　proportional　to　its　sensitivity　to　clay.　The　influencing　mechanism　of　clay　on　PCE　was　analyzed　from　the　structures　of　kaolin　and　bentonite　and　their　adsorption　characteristics　between　interlayer.　The　result　of　exploring　control　measure　showed　that　adding　the　synthesized　pre-adsorbent　can　effectively　inhibit　the　effect　of　clay　on　PCE　and　ensure　its　workability.