The effect of Ni cations and synthetic methods on the crystallinity, morphology, thermal stability and hydrophobic properties of carbonate-containing layered double hydroxides (LDHs) was investigated. The conventional hydrothermal treatment (CHT) and microwave hydrothermal treatment (MHT) methods were used to synthesize LDHs. The microwave treatment LDHs (MgAl-MHT and NiMgAl-MHT) have higher crystallinity and smaller crystal sizes than the conventional hydrothermal treatment LDHs (MgAl-CHT and NiMgAl-CHT). IR results indicate that the interactions of both OH(-)-CO(3)(2-) and CO(3)(2-)-CO(3)(2-) in NiMgAl-MHT are weaker. Furthermore, the thermal decomposition of OH(-) and CO(3)(2-) in the NiMgAl-MHT sample occurred earlier and faster than that of other LDHs. The contact angle values indicate that NiMgAl-MHT has the highest hydrophobicity. The influences of the LDHs on the thermal degradation and flame retardance of ethylene vinyl acetate copolymer (EVA)-LDH composites have also been studied in detail. NiMgAl-MHT has the more homogeneous nano-dispersed layers in EVA matrix. All composites enhance the thermal stability compared with the pure EVA because of the release of H(2)O and CO(2). Flame retardance of NiMgAl-MHT-EVA was obviously higher than that of the pure EVA and other composites.