Pr-Fe-B/Ta bilayer films were sputtered on glass substrates in a high vacuum magnetron sputtering system. Before sputtering the magnetic Pr-Fe-B thin films, Ta underlayers with two different crystal structures, hexagonal close-packed HCP(0002) and body-centered cubic BCC(110), were prepared at substrate temperatures of 300 and 600 $^{\circ}$C, respectively. With the Ta HCP(0002) underlayer, the Pr-Fe-B film showed significant in-plane oriented Pr $_{{2}}$Fe$_{{14}}$B phase and a small amount of perpendicular magnetic anisotropy (PMA) phases. The magnetic properties hence exhibited high nucleation field $H_{\mathrm{n}}$, coercive field $H_{\mathrm{c}}$, and large area in-plane hysteresis loop. Further replacing the Ta HCP(0002) underlayer with a Ta BCC(110) underlayer promoted the growth of columnar Pr-Fe-B grains. The typical hard Pr$_{{2}}$ Fe$_{{14}}$B phase with PMA was obtained. Low $H_{\mathrm{n}},$ $H_{\mathrm{c}}$, and small area in-plane hysteresis loop were consequently obtained. The PMA of the Pr-Fe-B/Ta bilayer film was also improved. The mechanisms to enhance the PMA of Pr-Fe-B/Ta bilayer films could be attributed to a lattice mismatch between the magnetic Pr-Fe-B layer and the Ta underlayers, where the smaller lattice mismatch at Pr$_{{2}}$ Fe$_{{14}}$B (00l)/Ta(110) interface promoted the (00l)-oriented Pr$_{{2}}$ Fe$_{{14}}$B planes to epitaxially grow on the Ta BCC(110) underlayer. Replacing the Ta BCC(110) underlayer with a Ta HCP(0002) underlayer just reduced the epitaxial effects and increased the pinning sites in the Pr-Fe-B magnetic films.