Al (OH) 3,sb2o3, zinc borate (ZB) and other inorganic flame retardants have been added to PVC cable materials, and their dosage has a great influence on the flame retardancy of PVC, which has been studied by many scholars at home and abroad. Some scholars have studied the effect of Sb2O3 and SB2O3/ZB compound flame retardant additive on the PVC Oxygen index. They found that with the increase of Sb2O3, the limit oxygen index of PVC cable showed a straight upward trend, when the amount of nano-Sb2O3 was more than 1.5, nano-Sb2O3 contributed more to the oxygen index of PVC than Micron-level Sb2O3. They also studied the oxygen index of PVC when the mass ratio of Sb2O3 and ZB was different, and found that the oxygen index decreased with the increase of mass ratio. That is to say, the more Sb2O3, PVC flame retardant performance, but because Sb2O3 price is more expensive, so the general addition of Sb2O3 is not very high, as long as you can guarantee a certain degree of fire resistance. And the addition of ZB can be used as a smoke-removing agent, the combination of ZB and Sb2O3 will make the PVC cable material with the appropriate oxygen index, but also has low smoke.