采用快速成核晶化法合成锌镁铝类水滑石（ZnMgAl-LDHs），以油酸钠为改性剂对LDHs进行湿法表面改性；通过FT-IR、XRD、FESEM、TG等对改性前后LDHs进行表征；考察改性前后LDHs的添加量对LDHs/软PVC复合材料阻燃及力学性能的影响。结果表明，油酸钠质量浓度为1.75 g/L，改性温度为65℃，改性时间为30 min，改性后LDHs的平均活化指数为99.65%。LDHs/软PVC复合材料的极限氧指数（LOI）值随LDHs添加量的增加而增大，改性后LDHs的阻燃效果明显改善；当LDHs添加量在0~10份（PVC为100份）左右，添加改性后LDHs的复合材料的拉伸强度和断裂伸长率均优于空白样；添加量在10~50份时，复合材料的断裂伸长率和拉伸强度均随着添加量的增加而下降，改性后LDHs的下降趋势明显弱于未改性LDHs。

ZnMgAl-LDHs layered double hydroxides (LDHs) is prepared by a rapid nucleation and crystallization method,and is surficial modified by wet method using sodium oleate as modifier.LDHs and modified LDHs both are characterized by FT-IR,XRD,FESEM,TG etc.The influences of the addition amounts of LDHs and modified LDHs on the flame retardant and mechanical properties of LDHs/soft PVC composites are investigated.The results show that the average activation index of modified LDHs is 99.65%,when the mass concentration of sodium oleate is 1.75 g·L^-1,the modification temperature is at 65℃ and the modification spends 30 min.The limiting oxygen index (LOI) of LDHs/soft PVC composites increases with the increase of addition amount of LDHs.The flame retardant property of modified-LDHs/soft PVC composites is better than that of LDHs/soft PVC.When the addition amount of LDHs modified or not modified is 0%~10% that of PVC,the tensile strength and elongation at break of modified-LDHs/soft PVC composites are both better than that of the blank samples.When the addition amount of LDHs modified or not modified is 10%~50%,both the tensile strength and elongation at break of composites decrease with the increase of mass fraction of LDHs,and that of modified-LDHs/soft PVC composites decrease slowly than that of LDHs/soft PVC composites.