With the increasing pace of exploration and enhanced oil drilling technology, especially with the deepening probe, well, ultra deep well, complex well, long cementing segment well, easy to leakage wells are increasing, conventional slurry system has cementing wells can not meet such requirements. The low-density slurry to protect and improve the quality of cementing oil and gas layers is important. A large number of documents and data show: cement, floating bead, micro silicon reasonable ratio test for optimization, you can get a large range of adjustable density, and cement pore structure has been improved, a significant reduction in permeability and low intensity increase dense slurry system. Experimental research was: the optimal dosage of dispersant in the range of 1.2 to 1.5%. Fluid loss additive content at 1.5%, water loss has been reduced to a range of low-density slurry required. Through the different formulations and different curing time of cement compressive and flexural strength obtained experimental comparison: join early strength agent can significantly improve the early strength of cement formulations, early strength agent added in an amount ranging between 1.2 to 1.8%. The resulting low-density formula is: Wei Sheng Class G cement + (water-cement ratio from 0.83 to 1.20) + floating beads (20 to 50%) + micro-silicon (13 to 23%) + fluid loss (1.5 to 2.0% ) + dispersing agent (1.2 to 1.5%) + early strength agent (1.2 to 1.8%). According to this formulation under a range obtained slurry system adjustable density range, has good stability, liquidity and certain thixotropic, low water loss, the early strength of many advantages, can significantly improve the quality of cementing, effectively prevent leakage and cementing of reservoir damage.