Based on the great advantages in low permeability reservoir development, horizontal well has been an important part of the development of shallow reservoir in Yanchang oilfield. For the characteristics of low temperature, shallow vertical depth and the horizontal seams creating in post fracture in this region, high strength and good sealing are required for the cement sheath. Through laboratory tests, a new type of chlorine-free composite M59S was selected, which was put with iron ion and aluminum ion in cement to form an early strength complex to greatly shorten the cement hydration time at low temperatures and improve the early strength of cement stone. A set of low temperature early strength slurry system is formed assisting by other additives. By the laboratory performance evaluation, this slurry system has a short thickening transition time, good stability and rheological characteristic, zero water precipitation and water loss less than 40mL. The compressive strength of cement stone reached more than 20MPa with ordinary pressure curing in the condition of 20℃ for 48h. The construction requirements of low temperature horizontal well cementation were satisfied. This low temperature early strength slurry system has good cementing effects in its application for shallow horizontal wells in the eastern part of Yanchang oilfield.