Abstarct: Given the importance of high-rise buildings in terms of financial and human issues, it is necessary to accurately assess the vulnerability of these buildings to various accidents. As the height of the building increases, the period of the structure increases and when a long period earthquake occurs, there is a possibility of increasing the vulnerability of the structure due to the intensification phenomenon. Due to the importance of the issue, a careful assessment of the impact of such a phenomena on the performance of the buildings should be done and their vulnerability should be examined by performing various analyzes. Assessing the performance level of a building with the help of fragility curves is the best way to calculate the potential damage. Using these curves, the fragility of different structures is investigated and using this data, a suitable solution can be provided to eliminate possible weaknesses. Therefore, three models of high-rise concrete buildings of 15, 25 and 35 floors with a similar plan and with a special moment frxame structural system are considered and are designed in Etabs 2016 software. These buildings are then modeled in OpenSEES software and IDA analysis is performed under long and short period earthquakes. Using the results of IDA analysis, fragility curves at different failure levels are plotted for all models. By comparing fragility curves and mean values of fragility, with and without long period earthquakes, the effect of earthquake frequency content on the seismic performance of high-rise buildings can be evaluated. Due to fragility curves, in general, the vulnerability of modeled buildings under long period earthquakes increases compared to short period earthquakes. As the intensity of the earthquake increases, the difference in fragility curves under the long period records and short period increases. At low failure levels this difference is small and at higher intensity earthquakes the difference is greater and at full failure levels it reaches its maximum.. Also, according to the values of fragility intermediates, the largest difference of intermediates in different failure levels is related to 25 story building.