The absorption and fluorescence spectra of Tb3+ and Eu3+ in LnP5O14 crystals at room temperture were observed. Based on absorption spectra and Judd-Ofelt theory, experimental and theoretical oscillator strengths were calculated. Series phenomenolo-gical intensity parameters were determined according to a least-square fitting. Then a calculation of the radiative transition probabilities and lifetimes of 5D3→7F5, 5D4→7F4 and 5D4→7F6 in TbP5O14, as well as 5D0→7F2 and 5D0→7F4 in EuP5O14 was carried out. We also obtain corresponding fluorescence lifetime by using time-resolved spectroscopy at various temperatures. The experimental results are in agreement with theoretical results. Our results confirmed that the lifetime of Tb3+ 5D3 depends mainly on the electric dipole-dipole cross relaxation between 5D3→5D4 and 7F6 →7F0.