Ultrasonic-assisted extraction (UAE) of oligosaccharides from lotus (Nelumbo nucifera Gaertn.) seeds (LSO) was studied in this paper. The three parameters, ultrasonic power (300~500W), solid to liquid ratio (g/mL) 1∶15~1∶25, and extraction time (30~50min), were optimized using the Box-Behnkens Design (BBD) with a quadratic regression model built by Response Surface Methodology (RSM). The order of three parameters on the LSO yield was as follows: solid to liquid ratio＞ultrasonic power＞extraction time. The highest oil yield, 1.13% (w/w), was obtained under optimal conditions for ultrasonic power, solid to liquid ratio, and extraction time at 320W, 1∶25, and 48min, respectively. The LSO yield extracted by UAE was significantly higher than that by using hot water extraction (HWE: 68.18%) and microwave-assisted extraction (MAE: 29.88%).