An optical imaging system, the optical imaging system sequentially comprising along the optical axis from an object side to an image side: a first lens (E1), a second lens (E2), a third lens (E3), a fourth lens (E4), a fifth lens (E5), a sixth lens (E6), and a seventh lens (E7). The first lens (E1) and the third lens (E3) each have a positive focal power; the second lens (E2), the fourth lens (E4), the fifth lens (E5), the sixth lens (E6) and the seventh lens (E7) each have a positive focal power or a negative focal power; an object side surface (S1) of the first lens (E1) is a convex surface, and an image side surface (S2) thereof is a concave surface; an image side surface (S4) of the second lens (E1) is a concave surface; an object side surface (S5) of the third lens (E1) is a convex surface; an object side surface (S13) of the seventh lens (E1) is a convex surface, and an image side surface (S14) thereof is a concave surface; the total effective focal length f of the optical imaging system and the entrance pupil diameter (EPD) of the optical imaging system satisfy f/EPD ≤ 1.5; and the central thickness CT7 of the seventh lens (E1) on the optical axis, the central thickness CT5 of the fifth lens (E1) on the optical axis, and half of the maximum field of view angle (HFOV) of the optical imaging system meet 1