The invention relates to an imaging system which comprises a first lens (E1), a second lens (E2), a third lens (E3), a diaphragm (STO), a fourth lens (E4), a fifth lens (E5), a sixth lens (E6) and a seventh lens (E7) which are sequentially arranged from an object side to an image side along an optical axis, and the first lens (E1), the second lens (E2), the third lens (E3) and the sixth lens (E6) all have focal power; the fourth lens (E4) has negative focal power, the fifth lens (E5) has positive focal power, and the seventh lens (E7) has negative focal power. The imaging system has excellent characteristics of ultra wide angle and the like, so that more photographing requirements can be met.