Solar　energy　is　considered　one　of　the　most　promising　energy　sources　for　the　degradation　of　pollutants　in　the　water　treatments.　An　innovative　solar　photo-thermochemical　system　involving　peroxydisulfate　(PDS)　as　an　oxidant　and　xenon　lamp　as　a　solar　irradiation　light　source　was　applied　with　hopes　to　degrade　organic　matters　and　alleviate　the　ultrafiltration　(UF)　membrane　fouling　when　treating　the　real　surface　water.　Moreover,　heat-activated　PDS　pretreatment　was　used　as　a　comparison　to　explore　the　respective　proportions　of　solar　light　and　heating　effects,　finding　that　solar　light　effect　dominated　the　activation　of　PDS　to　degrade　natural　organic　matters　(NOMs)　when　the　reaction　temperature　was　below　50　°C　and　they　both　contributed　to　the　production　of　free　radicals　at　the　temperature　of　＞50　°C.　The　results　indicated　that　solar-activated　PDS　pretreatment　significantly　alleviated　membrane　fouling　caused　by　Songhua　River　water　with　the　highest　transmembrane　pressure　(TMP)　reduction　of　approximately　69.6%　at　70　°C.　Organic　substances　(characterized　by　DOC,　UV254　and　the　maximum　florescent　intensity)　and　micropollutant　(atrazine)　in　the　feed　water　were　better　degraded　in　the　presence　of　solar　light.　Both　total　fouling　index　(TFI)　and　hydraulic　irreversible　fouling　index　(HIFI)　were　moderate　correlated　with　the　UV254　and　DOC,　whereas　remarkably　correlated　with　the　Fmax　of　component　2　(C2)　and　component　3　(C3).　In　addition,　no　significant　correlation　was　observed　between　fouling　indexes　(TFI　and　HIFI)　and　the　Fmax　of　component　1　(C1).　The　membrane　irreversible　fouling　was　attributed　to　the　accumulation　of　cake　layers　mainly　composed　of　protein-like　substances　on　the　membrane　surface.　Solar-activated　PDS　pretreatment　would　efficiently　degrade　the　protein-like　substances　and　terrestrially　derived　humic-like　matters　to　control　UF　membrane　fouling.　The　findings　are　beneficial　to　develop　new　strategies　for　membrane　fouling　alleviation　based　on　the　solar　irradiation　and　PDS　oxidation.　©　2020