The basic requirements of the wire tensioner winch for sealing are good sealing, safety and reliability, long life, compact structure, simple system, easy manufacturing and low cost. Most of the sealing parts are easily damaged parts, to ensure interchangeability, standardization, serialization. The type and use of sealing materials, sealing materials should meet the requirements of the sealing function. Due to the different sealing medium of the belt tensioner and the different operating conditions of the equipment, so the different adaptability of the sealing material is required. Requirements for sealing materials are generally: good material denseness, not easy to leak the medium; suitable mechanical strength and hardness; good compressibility and recovery, small deformation; high temperature does not soften, not degradation, low temperature does not solidify, not fragile.