The invention discloses low-density and high-strength 
cement paste, which is applied to cementing of wells tending to leak under a low pressure. The 
cement paste is prepared from the following components in parts by weight: 100 parts of 
oil well cement, 21-42 parts of hollow glass microbeads, 75-45 parts of 
coal ash, 8.9-14 parts of micro 
silicon, 3 parts of a 
filtration-
reducing agent, 0.8-1.2 parts of a dispersing agent and 130-136 parts of water. In the 
cement paste, glass microbeads are taken as main lightening materials, so that the density of low-density 
cement paste is lowered to 1.15-1.35 g / cm<3>, and the application arrange of the low-density 
cement paste is widened; by compactly piling cement particles, 
coal ash particles, glass microbead particles and micro 
silicon particles, the percentage of 
solid-phase particles is increased, and cement stone is dense, has high strength, high penetration resistance, high 
sedimentation stability and contribution to preventing of rush, and is free from concentration; and the cement paste does not contains any early strength admixture, the strength is enhanced by fully depending on compact piling of particles, the cement paste can be mixed with any fluid loss agent without damaging the fluid loss effect, and 
pollution on stratum is low.