Abstract: A four-effect-parallel-flow MED-TVC desalination experimental system was adopted to conduct performance experiments under TVC different suction positions in order to increase the MED desalination system performance and study the influence of TVC suction position variation on system performance.The experimental results show that variation in suction position of TVC has considerable effects on the MED system performance.The MED-TVC desalination system performance ratio increases first and then decreases with the suction pressure increases and compression ratio decreases.There is an optimal value and range which could make performance ratio get its maximum and higher values and 2.0- 2.3 is research result.Reasonable selection of suction position of TVC is imperative so as to make compression ratio within its optimal range and increase the MED desalination system performance.