Abstract: The efficiency of lignite power generation units is not desirable. However, burning pre-dried lignite, which is obtained by lignite pre-drying, is one of measures to improve it. Therefore, simulation model was established by Ebsilon according to the heat balance diagram of a typical 600 MW unit, and was used to compare variable load characteristics, the change regularity of main parameters and the thermal economy of the units burning pre-dried lignites with different design coals. Quantitative analysis was carried out, as well as the investment economy analysis. The purpose of research was to lay a theoretical foundation and pre-drying investment reference for variable load operation of the existing lignite power generation units to burn pre-dried lignite in production practice. The simulation results show that: the variable load regularity of each burning pre-dried lignite unit is basically identical to that of units with directly burning high-quality coal; when burning pre-dried lignite unit with lower moisture content of design coal reduces the load, the descent extent of boiler efficiency is more obvious, which indicates that burning pre-dried lignite unit with higher moisture content of design coal has better adaptability under variable load condition; the standard coal consumption rate of unit with high moisture content of design coal can be reduced by 5～7 g/k W·h when burning pre-dried lignite at different loads, which can still bring considerable benefits although the thermal economic improvement effect of unit discounts at low load.