Combining　a　negative　stiffness　mechanism　composed　of　tension　spring　with　a　linear　positive　stiffness　spring　in　parallel,　a　novel　quasi-zero　stiffness　vibration　isolation　systemwas　designed　which　can　be　used　to　isolate　low　or　ultra-low　vibration.　The　static　model　of　the　system　was　established　and　the　condition　of　quasi-zero　stiffness　characteristics　was　obtained.　The　fore-displacement　curves　of　the　tension-type　isolator　and　a　compression-type　isolator　were　compared.　The　effect　of　adjustment　of　vertical　spring　in　the　system　was　analyzed.　The　dynamic　equation　was　established　when　the　system　was　excited　by　a　harmonic　amplitude　on　the　displacement　and　the　equation　was　solved　by　using　Harmonic　Balance　method.　The　displacement　transmissibility　curves　of　the　tension-type　and　the　compression-type　isolators　were　also　compared.　The　effect　of　the　main　parameters　on　response　of　the　system　was　explored.　ADAMS　model　was　established　and　the　static　model　was　proved　to　be　correct.　The　vibration　simulation　results　prove　that　the　quasi-zero　stiffness　system　has　greater　advantage　than　linear　system　in　low　or　ultra-low　vibration　isolation.　©　2018,　Editorial　Department　of　JOURNAL　OF　MECHANICAL　STRENGTH.　All　right　reserved.