Sabah Snake Grass (Clinacanthus nutans) is interesting traditional medicine because of pharmacology characteristics that contain rich in phenolic content and antioxidant. The aim of study was to determine the optimum yield and exhaustive time extraction using Peleg’s model. Qualitative and quantification test for detection of orientin and vitexin using method of high performance liquid chromatography (HPLC). Based on the results obtained, the optimum concentration for orientin (0.72 ± 0.002 mg/g) and vitexin (2.10 ± 0.13 mg/g) were observed at 18 h of extraction (texhaustive). The optimum extraction parameters for optimum recovery of phenolic content and antioxidant activities from the leaves of Clinachantus nutans were determined using response surface methodology (RSM). The total phenolic content (TPC) was analyzed using the Folin-Ciocalteu method and antioxidant activities were evaluated through 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, 2,2’-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radical scavenging activity and the ferric reducing antioxidant power (FRAP) assay. A central composite rotatable design (CCRD) was employed to investigate the effects of ultrasonic frequency (X1: 25 - 40 kHz), temperature (X2: 40 - 80ºC) and solid-to-liquid ratio (X3: 10 - 30 ml/g) on the recovery of TPC (Y1) and antioxidant activities of DPPH (Y2) and FRAP (Y3). The optimal parameter achieved based on combination of extraction parameters: X1 = 25 kHz sonication capacity, X2 = 80ºC temperature and X3 = 30 g/ml of solid-liquid ratio. These optimum conditions yielded TPC of (25.09 mg GAE/g), DPPH (66.85%), and FRAP (9.44 μmol TE/g). The optimum values of TPC and DPPH from this study are comparable with green tea (benchmark). Our results revealed that distilled water may be a good choice for extracting antioxidant activity of Clinacanthus mutans. Concentration of orientin and vitexin compounds were extracted during optimization exhibited lower than the finding from Peleg model. Prolonged extraction at high temperature during optimization may degrade flavonoid and phenolic acid compounds. However, the concentration of extracted compound (orientin and vitexin) from the optimum parameters had produced high in phenolic content and antioxidant activity. In conclusion, the application of Peleg model was able to determine the extraction exhaustive time at the maximum extract yield. In addition, this study proved that the application both models (RSM and Peleg) have been successfully be able to provide the optimum extraction parameters with high total phenolic content and antioxidant activity.