Disclosed is a diesel engine variable-altitude boost pressure control method. Through a two-level adjustable booster controller ECU, according to change of altitude, diesel engine rotation speed and loads, opening of a high-pressure stage VGT vane of a two-level adjustable booster and opening of a high-pressure stage turbine regulating valve and a low-pressure stage turbine regulating valve are controlled in real time, optimal control is conducted on boost pressure in a variable-altitude and variable-working-condition mode, and the purpose that in the 0 m-5500 m altitude range, all performance indicators of a diesel engine are always kept the same as the performance under the plain conditions is achieved. The mode that feedforward control and fuzzy PID control are combined is adopted for the diesel engine variable-altitude boost pressure control method, and the boost pressure can be adjusted in real time according to change of altitude and working conditions of the diesel engine, so that the requirements for best power performance and fuel economy in the steady state working condition and the transient state working condition are met, the objective that power of the diesel engine at the altitude 5500 m fixed point is recovered to 95% or above that on plains is achieved, turbo lag is relieved, and pumping loss work is reduced. Meanwhile, the problems of gas compressor surges, turbine overspeed, excessively high turbine-front discharge temperature and the like are avoided.