In this present study， surfactant-mediated ultrasound-assisted extraction（S-UAE） was applied to extract pectin from citrus peel. The effect of extraction pH， ultrasound time， and liquid solid ratio （LSR） on yield， galacturonic acid （GA） content， and degree of esterification （DE） of extracted pectin from the citrus peel was investigated. The highest pectin yield （but only 17.1%） was obtained under pH of 0.6， ultrasound irradiation time of 15.0 min， and LSR of 21.0 mL/g by using response surface methodology. And on this basis， synergistic actions by surfactants and ultrasound assisted extraction were studied for pectin extraction in the work. When sodium dodecyl sulfate （SDS） （8 g/L） was added to the extraction media before ultrasound irradiation， the yield of pectin increased by 55.0% （PY of 26.4% ± 0.8%） compared with control. Furthermore， the yields and physicochemical properties， e.g. GA content， DE and average molecular weight（Mw） of extracted pectin by using conventional extraction， UAE， and S-UAE were compared. So， S-UAE has been proved to be an efficient and cost-effective method for citrus peel pectin extraction. In addition， high methoxyl citrus pectin was used to produce an amidated pectin under low temperature， parameters such as reaction temperature， pH value and pectin concentration were studied. The results indicated that DA 13%-22%， DE 29%-39%， GA 69%-84%， intrinsic viscosity 136-172 mPa·s and Mw 148-173 ku of the amidated product under the optimized conditions （reaction temperature 10 ℃， pH 11.5， pectin mass concentration 20 g/L， and reaction time 100-180 min）， meet the domestic and foreign standards requirements. This study provides a positive and useful reference for the high value utilization of citrus by-products in China.