The invention discloses a deep sea photoelectric composite cable for a mooring type marine observation system. The deep sea photoelectric composite cable includes power units, stainless steel fiber units, a taped covering, an inner sheath, an armor layer and an outer sheath, wherein the plurality of power units and the plurality of stainless steel fiber units are stranded to form a cable core; the taped covering sleeves the cable core; the inner sheath is extruded on the outside of the taped covering; the outside of the inner sheath is stranded with the armor layer; and the outer sheath is extruded on the outside of the armor layer. For the photoelectric composite cable, the inner and outer sheathes utilize the anti-fatigue seawater-proof elastomer material so as to guarantee that the inner and outer sheathes are high in dynamic performance, fatigue performance and environmental performance; and the armor layer is formed through stranding of galvanized high-carbon steel wires which are designed through torque balance so as to guarantee that the armor layer is high in mechanical performance and seawater corrosion resistance and is high in dynamic performance and fatigue performance.