NOVELTY - A hollow pumpkin-like copper oxide (CuO) nanomaterial is prepared by weighing soluble copper salt such as copper acetate to prepare solution A using deionized water; weighing urea to prepare solution B using deionized water; adding solution A into solution B to form precursor solution C; transferring precursor solution C into sealed screw thread bottle, placing into ultrasonic cleaner filled with tapping water, and ultrasonically radiating for filtering settlement, and washing using water and anhydrous ethanol respectively; and placing settlement into oven and heating.    USE - Method for preparing hollow pumpkin-like copper oxide (CuO) nanomaterial (claimed) used for fields of catalysis, antibacterial, solar cell and sensor material.    ADVANTAGE - The prepared nanomaterial has hollow gradation structure, has no conglobation and is singly dispersed. The method has simple and clean process and is environment friendly. It does not use any surfactants and organic solvents, has low reaction temperature and short reaction time. The method also saves energy, has easily obtained raw material and low cost, and it is suitable for industrial production.    DETAILED DESCRIPTION - Hollow pumpkin-like copper oxide (CuO) nanomaterial is prepared by:    (A) weighing soluble copper salt (1 mmol) such as copper acetate to prepare solution A using deionized water;    (B) weighing urea to prepare solution B using deionized water, where mol. ratio of copper salt to urea is 1:2.5-1:7.5;    (C) under agitation condition, adding solution A into solution B to form precursor solution C, where total volume of solution is 60 mL, and agitating for 10 minutes;    (D) transferring precursor solution C into 100 mL of sealed screw thread bottle, placing into ultrasonic cleaner filled with tapping water of 80 plus minus 10 degrees C, and ultrasonically radiating for 1-3 hours, where power of ultrasonic wave is 50 W;    (E) taking out to naturally cool into room temperature, filtering settlement, 2-3 times washing using water and anhydrous ethanol respectively; and    (F) placing settlement into oven and heating for 6-12 hours, where temperature is 40-60 degrees C, and collecting black product to obtain nanomaterial.