Lens, lamp adopting same and design method of lens

The invention relates to the technical field of illumination, in particular to a lens, a lamp adopting the same and a design method of the lens. The lens is provided with an incident area and an emergent area, a reflection area is formed on the outer side wall face between the emergent area and the incident area, and the emergent area comprises a first emergent area and a second emergent area surrounding the exterior of the first emergent area; the second emergent area comprises a base level and a plurality of protruding units arranged on the base level, the base level is provided with a largeend and a small end, and the distance between the small end and the large end of the base level is H1 in the direction of the lens optical axis and is D1 in the direction perpendicular to the lens optical axis, wherein D1/H1 meets the formula of 3>=D1/H1>=1.1; and the protruding units are arranged around the lens optical axis, and at least one part of light rays intersect after the light rays located on the plane passing