The ultra-heavy oil reservoirs of Fengcheng Oilfield in Xinjiang are continental braided fluvial facies with strong heterogeneity. The permeability variation coefficient is 0.7-0.9，and the distribution density of muddy interlayers is 2.4 strips/m. As a result，SAGD well groups have some prominent problems，such as low producing degree of the horizontal section and uneven expansion of steam chambers. In virtue of the mechanical properties and the dilation mechanism of reservoir rocks，this paper studies the controllable upgraded dilation technology by using large-scale physical simulation and coupled numerical simulation of rock mechanics under the true triaxial in-situ stress，and specifies the optimal dilation methods and parameters for breaking the interlayers between injection and production horizontal wells，breaking the interlayers above steam injection horizontal wells，and producing multilateral well sections of SAGD reservoir. According to the results，the oil sands of Well Block A of Fengcheng Oilfield has a strong dilation effect under low confining pressures. A complex dilation area can be formed under the effect of both constant pressure and stepwise raised pressure，and the maximum dilation volume is as high as 7%. Under the condition of reasonable dilation parameters，the dilation radius of ultraheavy oil reservoirs of Fengcheng Oilfield can reach 10-15 m. Compared with the traditional fast and uniform start-up technology，the technology for the upgraded dilation of SAGD reservoirs with strong heterogeneity and ultra-heavy oil can realize better reservoir adaptability and significantly increase oil production.