The above results on electronic properties in Co-doped NaFeAs are consistent with that of Co-doped 122 or 1111 systems. We know that phosphor doping in BaFe 2 As 2 induces supercnductivity with Tc=30 K, much higher than the Tc=22K of Co-doped BaFe 2 As 2 . When we dope NaFeAs with P, our results do show clear transition temperature high up to 33 K. It is clearly shown both in the resistivity curve (Fig. 2(a)) and magnetization data (The inset of Fig. 2(a)). The superconducting transition is very sharp with the transition width smaller than 1 K. What is the cause of such a high transition temperature remains an open question. Mizuguhci et al. proposed in their report that the anion height is crucial in determining the Tc of the iron-based superconductors.[26] In P-doped NaFeAs, the Fe has the valence of 2+, and no nominal carriers are introduced into the iron layer, which may not cause disorder in the iron layer. But according to their strict requirement, no dopings can be done on anion site either, ie. no substitution of P for As should be done if the rules are satisfied before P-doped NaFeAs is put on the symmetric curve they proposed. On the other hand, regular tetrahedron of FeAs 4 lattices in the FeAs block are believed to be one key point in achieving higher Tc[27, 28]. More and more results are consistent with the prediction and obey the rule. In 111 system, pressure effect on LiFeAs is sys- tematically studied, and Tc decreases with increasing pressure.[29] The lattice parameters are summarized based on Rietveld refinement and it is found that the FeAs 4 tetrahedron is highly distorted and the pressure further enhances the distortion so the Tc decreases. As for NaFeAs, the Tc of NaFeAs is 23 K,[20] and refinement results show us NaFeAs possesses a more regular tetrahedron with the basic difference that the radii of Na is bigger than that of Li and it forms a less distorted environment.[22] The P-doped NaFeAs superconducts at 33 K, so we believe that the FeAs 4 tetrahedron here is more regular than that in Na-deficiency polycrystalline NaFeAs.[22] We should emphasize the Tc is the highest in all Co-doped or isoelectronic element-doped systems. In previous report on NaFeAs pollycrystalline samples, the maximum Tc of 31 K is observed when the pressure of 3.0 GPa is applied.[30] As we know the pressure effect on iron-based superconductors are complex with two major cate- gories: one type is that pressure enhances the Tc of the samples while another is that the pressure firstly enhances then suppresses the Tc. These behaviors are intimately related to the lattice parameters and configuration of FeAs 4 tetrahedron. Considering such effect, we expect possible higher Tc to be realized in the work studying the pressure effect on P-doped NaFeAs crystals. Further work on the lattice parameters and pressure effect on the P-doped