The invention relates to a capping anti-evaporation technology and especially relates to a floating ball capable of preventing water surface evaporation of a plain reservoir and a logging dam in an arid area. The floating ball is characterized in that the sealed hollow floating ball is made of plastic, wherein the plastic is composed of polyolefin with an added inhibitor, the inhibitor occupies a weight percentage of 2.5%-3.7% in the weight of a floating ball shell, and the rest part is made of the polyolefin; a balance weight is firmly connected to the bottom of an inner shell of the hollow floating ball; the radius of the hollow floating ball is 40-60 mm; the ball shell thickness of the hollow floating ball is 1.2-1.8 mm; and the hollow floating ball is light grey. The floating ball has the advantages that the structure is simple; the floating ball floats on a water surface and does not require connection and fixation; the floating ball has high strength and a low gravity center; under external force of winds and waves, the floating ball does not turn over vertically easily; anti-evaporation and water-saving effects are good; the floating ball is highly resistant to the winds and waves, collision, freezing and thawing, leakage, ultraviolet light and water erosion; the manufacture cost is low; and practicability is high.