The invention relates to a functional reliability enhancing method of a siphon valve on a polymeric centrifugal microfluidic chip, in particular to a siphon valve of a centrifugal microfluidic chip and an application method of the siphon valve, in order to fully fill a siphon with liquid before siphon flow in the siphon valve, avoid hydrophilic treatment on surfaces of materials and guarantee long-term functional stability of the chip. The purpose is to guarantee the functional stability of the siphon valve in the surface-lyophobic microfluidic chip obtained by processing polymer materials; according to the method, the siphon is filled with the liquid by depending on received Euler force during accelerated rotation of the chip, so that spontaneous capillary flow and material-surface hydrophilic treatment required in the process that the siphon valve on the polymeric centrifugal microfluidic chip is filled with the liquid are effectively avoided, and long-term functional stability of the chip is guaranteed. The siphon valve and the application method have the advantages of simple process, high reliability and easiness in implementation.