Under selective excitation 3P0 state of Pr3+ ion in YPO4, the emission spectra and fluorescence decay curves are measured at different concentrations and temperatures. The origin of the spectral line located at 613.2 nm has been discussed and assigned to be the 1D2 (gamma 3)-->3H4 (gamma 5) transition. The different concentration dependence of emission intensities of levels 3P0 and 1D2 has been studied. Using static model, the fluorescence decay curve of 1D2 level is fitted, and the result shows that the cross-relaxation caused by the interaction of dipole-quadrupole between adjacent Pr3+ ions results in the concentration quenching.