The conditions for the extraction of effective substances from the stem of Opuntia ficus-indica were optimized by a response surface methodology. The total extract yield was maximized under the temperature of $97.77^{circ}C$, at a time duration of 145.82 min and a water to sample ratio 16.59 mL/g. Moreover, the optimum conditions for the extraction of effective substances were as follows: $84.95^{circ}C$, 156.50 min and a water/sample ratio of 7.46 mL/g for the phenolics content; and $97.11^{circ}C$, 139.03 min and a water/sample ratio of 10.91 mL/g for the pectin content. The range of optimum extraction conditions in consideration of the physicochemical properties of the extracts were shown to be as $95-100^{circ}C$ as the extraction temperature, 120-180 min as extraction time and a water to sample ratio of 5-18 mL/g.