The invention relates to an economic day and night high definition zoom lens, and a control method thereof, belonging to the lens field. The economic day and night high definition zoom lens is applied to an intelligent security video shooting system, and has the characteristics of high optical index, large optical target surface, and resolution factor no less than three megapixels. In a technical scheme, the optical system of the lens is successively provided with a front set of negative focal power, and a rear set of positive focal power along a light incident direction; a changeable diaphragm is arranged between the front set and the rear set; the front set is successively provided with a negative crescent lens, a double concave aspheric lens and a double convex lens; the rear set is successively provided with a positive crescent lens, a double convex lens, a plano-concave lens and a double convex aspheric lens. According to the invention, the focal power of the front and rear sets is reasonably distributed in a retrofocus type optical structure, allowing a whole optical structure to be insensitive; the aspheric lenses enlarge the angle of a visual field, and rectify a lens image difference, thereby meeting fine definition video shooting requirements.