The photoluminescence (PL) transitions of the dilute-bismide InPBi originate mainly from the defect-related processes, and manifest the properties of long wavelength, broad linewidth and strong emission. To further clarify the PL efficiency issues, we carry out excitation power-dependent PL spectral analyses on a series of InPBi samples with different Bi compositions in this work. The PL lineshape changes significantly and the dominant emission redshifts as the Bi composition increases. Meanwhile, the excitation power-dependent evolution of the PL integral intensity indicates that the PL efficiency enhances firstly and then drops as the Bi composition rises, and reaches the maximum with a Bi composition of 0.5%. The enhancement of the PL efficiency is ascribed to the Bi trapping holes to lower the nonradioactive recombination on one hand, and to the Bi surfactant effect on the other hand. Nevertheless, the high Bi component brings excessive impurities and the Bi-related advantages are suppressed, which results in low PL efficiency. These results are beneficial to the understanding of the infrared emission performance of InPBi and suggest InPBi as a potential semiconductor for infrared optoelectronic applications.