The invention discloses a monitoring camera with a high resolution ratio. The monitoring camera is composed of six spherical lenses, wherein the six spherical lenses sequentially include the first lens with negative focal power, the second lens with position focal power, the third lens with positive focal power and a convex face facing an image side, the fourth lens with positive focal power, the fifth lens with negative focal power and a convex face facing the image side and the sixth lens with positive focal power from an object side to the image side. The fourth lens and the fifth lens are bonded together to form a bonding lens, an aperture diaphragm STO is arranged between the second lens L2 and the third lens L3, a flat optical filter F with zero focal power is arranged between a camera body and an image surface IMA, and the effective focal length f of the camera and a rear work distance BFL should meet the following condition that the result obtained after f is divided by BFL is larger than 0.5 and smaller than 1.5. Compared with the prior art, the monitoring camera is simple in structure and high in cost performance, the resolution ratio reaches more than five million pixels, the relative aperture is not smaller than 1/1.6, the relative illumination of a full view field approaches 70% or more and the monitoring camera is suitable for large-scale production.