In this paper, monodispersed CdTe quantum dots are synthesized by soft chemical method. Meanwhile, mercury cadmium telluride (Hg_xCd_1-xTe) quantum dots with the quasi continuous visible to near-infrared spectrum are prepared by ion exchange adjusting the concentration of Hg²⁺. The variable temperature photoluminescence and self-absorption characteristics of near-infrared Hg_0.33Cd_0.67Te quantum dots are deeply analyzed. The results indicate that the fluorescence intensity of Hg_xCd_1-xTe quantum dots decreases linearly with the increase of temperature (0～100 ℃). The spectral line broad and the peak position has a red-shift (12 nm). The partial overlap of absorption and emission spectra of quantum dots leads to self-absorption. The increase of self-absorption results in decrease of photoluminescence intensity while the concentration of quantum dots increases.