A convex-Fresnel LED lens and a LED assembly thereof are revealed. The lens is a Fresnel lens whose optical surface on a forward side thereof is a convex surface having draft with vertical shape so that the lens in the LED assembly concentrates light emitted from a LED chip to generate light whose peak intensity is an elliptic distribution pattern. Moreover, the lens and the LED assembly thereof satisfy certain conditions. Thereby, light from the LED chip is gathered by a single lens to form a preset specific distribution pattern and is satisfying requirement of the ratio of the luminous flux that is larger than 85%. The convex-Fresnel LED lens and a LED assembly thereof are applied to lights and flashlights in mobile phones or cameras.