The photon upconversion (UC) can realize the conversion of low-frequency photons to high-frequency photons. UC based on triplet-triplet-annihilation (TTA) has the characteristics of low threshold excitability, high quantum yield, and wide spectral conversion range, which have drawn broad research interested in the world. In this paper, two kinds of porphyrin complexes (named as PdOEP and PdBrTPP, respectively) were chosen as the sensitizer doped with p-DHMPA (as the emitter) to set up the TTA-UC research models. The absorption, fluorescence and phosphorescence spectra, as well as the upconversion spectra, were measured respectively. The relationships between triplet properties and the upconversion emission were discussed. Also, the relationship between the singlet-triplet energy level difference (ΔE_ST) of the sensitizer and their intersystem cross-section is discussed. And lastly, the relationship between the triplet energy level difference (ΔE_TT) from sensitizer to the emitter and the triplet-triplet energy transfer (TTET) is discussed. The results show that PdBrTPP has longer triplet lifetime (173.13 μs) than PdOEP (109.21 μs) and larger molar absorption coefficient (10.8 cm^-1·mmol·L^-1) than PdOEP (3.0 cm^-1·mmol·L^-1). Meanwhile, the quenching constant (k_q) of PdOEP/p-DHMPA (1.64×10^-3 μmol·L^-1·s^-1) is larger than PdBrTPP/p-DHMPA (6.53×10^-4 μmol·L^-1·s^-1); moreover, the threshold excitation intensity (I_th) of PdOEP/p-DHMPA (22.40 mW·cm^-2) is smaller than PdBrTPP/p-DHMPA (29.78 mW·cm^-2). All of these results in the upconversion efficiency (Φ_UC) of PdOEP/p-DHMPA (28.3%) is larger than PdBrTPP/p-DHMPA (26.8%). Therefore, it has been proved that the most important influence on the Φ_UC value is depended on the triplet energy level (E_T1) of sensitizer. Those porphyrin palladium sensitizers with higher triplet energy-levels can obtain high upconversion efficiency, regardless of difference among the molar absorption coefficient and the triplet lifetime. However, when using the overall upconversion ability (η) to revalue the upconversion processes, PdBrTPP has higher molar absorptivity than PdOEP, which can result in more absorbance. The total upconversion capability (η) of PdBrTPP is 3.4 times larger than PdOEP. Therefore, increasing the molar absorption coefficient of the sensitizer could be a feasible strategy to enhance the TTA-UC performance.