The overall effect of sealing the packaging has a very important role. Sealed plastic containers divided into four main ways, namely the bundle sealing, adhesive sealing, physical sealing and filling and sealing. They have their own characteristics. Bundling seal means the product can not be sealed, but its use is very wide, has a high degree of freedom. Low adhesive strength of adhesive sealing, but it is widely used. More complex structure of the physical sealing, but it has a wide variety of functions. Used in the filling and sealing gaskets are susceptible to damage, but it has a good seal. This paper analyzes the principles of their seal，which allows you to choose different sealing materials and the corresponding sealing structure to meet a variety of packaging needs.