The purpose of this study is to derive an estimation equation for calculating the lag time for ammonia load adaptation of methanogens during anaerobic digestion and to derive model coefficients using the results derived from the batch experiment results. Pig manure is known to be a representative substrate that inhibits the normal operation of the anaerobic digestion process by accumulating ammonia. AMPTS (Automatic Methane Potential Test Systems) equipment was used in the laboratory to determine whether methane bacteria can be suppressed and applied to the high concentration of ammonia in general pig manure and the operating factors for operating an on-site anaerobic digester at a pig farm. The methane production rate before adaptation to ammonia concentration is 0.68 L/gVS at TAN 2,700mg/L, while the microorganism after adaptation shows a generation rate of 0.82L/gVS at TAN 4,250mg/L. The delayed phase length (λ) range from 45 to 99 days in unadapted microorganisms, showing that methane production is possible without a delayed phase when using adapted microorganisms. The modified Gompertz model applied in this study not only shows a difference in the λ value, which represents the lag time, depending on whether the microorganisms adapt, but also shows a larger difference in Pm1, which represents the amount of methane production by stage, while the half-saturation constant K and the maximum gas in the second stage show a greater difference. The production rate, Rm, changes depending on the organic matter load and shows similar values ​​regardless of whether the microorganisms have adapted or not.