In this paper, we investigated the crystal quality of Mercury Cadmium Telluride (HgCdTe) materials in the key avalanche region of avalanche photodiode detectors (APDs) with MWIR PIN structure. We simulated the entire process of the PIN APD device on the experimental materials and used differential Hall testing and differential minority lifetime testing to evaluate the material’s real crystal quality in the key avalanche area. It is found that the crystal quality of the avalanche region under the optimized process is good. Its Shockley-Read-Hall (SRH) lifetime is 20.7 μs, which can be comparable to that of the primary HgCdTe materials. This meets the development requirements for high-quality MWIR HgCdTe avalanche devices. Additionally, based on the obtained SRH lifetime in the avalanche region, we conducted corresponding two-dimensional numerical simulations on HgCdTe APD structural devices to determine the theoretically optimal dark current density of 8.7×10^-10 A/cm².