For the development of practical products, valves such as orifice, double-inlet and multi-bypass in the pulse tube refrigerators, should be replaced by other more reliable structures. Potential choices are long thin tube, orifice or nozzle. In this paper, the difference between nozzle flow and orifice flow is analyzed. Their similarities are that they result in a similar reciprocal movement at hot end of the pulse tube; their differences are that their flow rates have different characteristics. According to state-flow theory, nozzle flow coefficient has a positive feedback to flow rate while orifice has no relation to flow rate generally. Further analysis shows this feature of nozzle will result in large refrigeration with the same pressure ratio and reservoir coefficient, which explains the reason that even lower temperature and a larger refrigeration amount can be obtained when symmetry-nozzle is used instead of orifice. Experiments of miniature pulse tube refrigerator show that symmetry-nozzle instead of check valves can improve the performance of pulse tube refrigerator effectively, which is also verified by calculation. But with Re number increasing, this advantage becomes unclear. This is explained both in analysis and in low frequency experiments.