The aim of this study is to estimate an Inflation-output Trade-off with Triangle model in Pakistan and other objective of this study also investigate a Time instability of inflation-output trade-off with triangle model in Pakistan using Time Series data over the periods of 1971-2016 in case of Pakistan. For this purpose we used a three step methodology to estimate an inflation-output tradeoff with triangle model such as Unit root Analysis, Cointegration Analysis and Error Correction Model. Dynamic of inflation has significant impact on output containing different two dummy variables in inflation. Empirical finding of this study shows that long run and significant relationship exist between inflation and supply variables such as oil prices and nominal exchange rate but no long run relationship exist between inflation and output gap. Output gap has positive and significant impact on inflation in short run but supply variables have no impact on inflation dynamic in short run. The environment of inflation is important to determine the relationship between inflation and output. Supervisor:- Dr. Abdul Qayyum