An efficient multi-component synthesis of indazolophthalazine derivatives through the reaction of phthalhydrazide, 2-hydroxynaphthalene-1,4-dione or 2,5-dihydroxycyclohexa-2,5-diene-1,4-dione and active carbonyl compounds under ultrasonic irradiation is reported. This chemistry provides an efficient and promising synthetic strategy to diversity-oriented construction of the indazolophthalazine skeleton with potential biological activities.