The dislocation density of MBE grown Hg 1-xCd xTe on ZnCdTe substrates was studied. It was found that the dislocation density in Hg 1-xCd xTe was sensitive to the damage layers of ZnCdTe substrates, growth conditions of HgCdTe as well as compositions. By optimizing the substrate preparation procedures and growth conditions, the averaged EPD value of 4.2×10 5cm -2 with the standard deviation of 3.5×10 5cm -2 was obtained, close to the dislocation density limit of substrate. The reproducibility was good with a yield of 73.7% as screened by dislocation density. The results should be able to meet the requirements for FPAs of high performance.