The influence of growth conditions of liquid phase epitaxy on the composition gradient of HgCdTe was studied, and the growth model of liquid phase epitaxy (LPE) of HgCdTe was established. HgCdTe with positive composition gradient was grown by slider liquid phase epitaxy by changing the mercury loss rate. The positive composition gradient structure of HgCdTe grown under the growth condition of specific mercury loss was confirmed by corrosion thinning spectrum and secondary ion mass spectrometry (SIMS). The experimental results show that the HgCdTe with positive composition gradient had the similar surface morphology and infrared transmission spectrum curve to the traditional HgCdTe with negative composition gradient; and it had high crystal quality, with a full width at half maximum (FWHM) of X-ray diffraction(XRD)double-crystal rocking curve of 28.8 arcsec.