Under the existing cementing slurry technology，ensuring the long-term stability of wellbore integrity is facing challenges，especially the conventional slurry with low density. After perforation，the integrity of cement stone is seriously damaged，resulting in sealing failure，poor cementing quality between cement stone and casing or well wall，and channeling is easy to occur. In view of the above problems，the elastic agent（RES-1）was prepared by using epoxy resin and anhydride curing agent as raw materials，the liquid fiber was used to increase the strength and toughness of cement paste，and the nano liquid lightening agent was used to improve the settlement stability of cement slurry. The comprehensive performance evaluation of elastic sealing cement slurry with low density was carried out. The results showed that RES-1 could reduce the elastic modulus and improve the deformation capacity of cement paste. The optimum dosage was 10%. The elastic sealing cement slurry system with low density （1.5 g/cm³）had good rheology. The water loss was less than 50 mL and the linear expansion rate reached 0.45%，which could effectively inhibit the generation of micro annulus and micro gap. The elastic sealing cement slurry with low density had good compactness，flexibility and elastic deformation ability. Compared with ordinary cement slurry with low density，its permeability and elastic modulus were reduced by 69.5% and 78.4%，and its compressive strength and flexural strength were increased by 61% and 87.9% respectively. The elastic sealing cement slurry with low density could effectively increase the long-term sealing capacity of cement sheath and improve cementing quality.