Zirconium-based alloys with different Nb and Fe addition ratios were treated by β-quenching at 1050 oC for 0.5 h and the followed annealing at 560 oC for 10 h; then their microstructure and second phase particles (SPPs) were examined by high-resolution transmission electron microscopy (HR-TEM) equipped with an energy dispersive X-ray spectroscopy (EDS). Results show that with the increasing of Nb addition and the Nb/Fe ratios, SPPs Zr(Fe,Cr)2 with a hexagonal close packed (HCP) structure in Zircaly-4 transform to SPPs Zr(Nb,Fe,Cr)2 with a hexagonal close packed structure; meanwhile the Nb/Fe ratio of Zr(Nb,Fe,Cr)2 is increased too. SPPs βNb with a body center cubic structure could be observed besides HCP-Zr(Nb,Fe,Cr)2 precipitates when Nb contents and Nb/Fe ratios are high enough