OBJECTIVE： To study the relationship between cisplatin-resistant of human ovarian cancer cells （SKOV3） and Toll-like receptor 9 （TLR9） under hypoxia. METHODS： Immunofluorescence method was used to detect the TLR9 expression in rupture and intact membranes SKOV3. SKOV3 was taken， adding cisplatin， then CCK-8 was used to detect cell inhibition rate after 6， 12， 24 h of added into TLR9 specific agonists CpG-ODN 2006 （group A） and its isotype control CpG-ODN 2006 control （group B）. SKOV3 or SKOV3 pretreated by 0 （not added）， 1， 10， 102， 103 μmol/L TLR9 specific antagonist chloroquine for 3 h were taken， adding cisplatin， cell inhibition rate was detected after 24 h of added into SKOV3 normoxia （21％ O2）， hypoxia （1％ O2） incubating 6，12，24 h， HICR under hypoxia in pretreatment was calculated. Western blot method was used to detect the multidrug resistance associated protein （MRP） expression in SKOV3 under the conditions of normoxia 24 h cell supernatant （group C）， hypoxia 24 h cell supernatant （group D）， hypoxia 24 h cell supernatant+10 μmol/L chloroquine （group E）. RESULTS： TLR9 was expressed in both cell membrane and cytoplasm of SKOV3. Compared with group A， cell inhibition rate in group B was decreased （P＜0.01）. Compared with normoxia cell supernatant， cell inhibition rate was decreased after hypoxia cell supernatant （P＜0.05）. Compared with not added chloroquine， adding 10， 102 μmol/L chloroquine can obviously decrease HICR （P＜0.01）， and the most significant decrease was showed when using hypoxia 24 h cell supernatant+10 μmol/L chloroquine. Compared with group C， MRP expression in group D was strengthened （P＜0.01）； compared with group D， MRP expression in group E was weakened （P＜0.01）. CONCLUSIONS： TLR9 receptors can be activated under hypoxia， and cause SKOV3 to cisplatin-resistance， the effect may be related with up-regulating MRP expression.