New psychoactive substances (NPS) are emerging continuously, as the crackdown against traditional drugs becomes stricter. Metabolites of NPSs and the unchanged drugs enter wastewater through urine and are collected and treated by wastewater treatment plants before being discharged into the aquatic environment. Based on previous research, solid phase extraction (SPE) and ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) were used and the detection method of 11 NPSs was optimized. Influences of wastewater pretreatment procedures, including SPE columns; pH values of water samples; and processes of flushing and redissolving on NPS recoveries were compared. It was shown that the best recovery was achieved when Oasis MCX columns were used and the pH value of wastewater samples was adjusted to 2. A flushing process with 2 mL water at pH=2 followed by 2 mL methanol was needed. Redissolution of the residue after evaporation was best achieved with 400 μL of a 20% methanol water solution. It