Abstract: In order to study the temperature development characteristics and structural response of the portal frame under different fire scenarios, four localized fire tests and one destructive spreading fire one were carried out on a scaled portal frame structure model. The heat release rate (HRR), ambient temperature, steel component temperature and structural displacement were measured. The test results show that the temperature rise characteristics of structures under local low-power fire are different from those of high-power fire. The local low-power fire is fuel-controlled combustion, and the upper flue gas temperature is high, while the lower temperature is low. In high-power fire, the upper flue gas temperature is lower and the lower part is higher when the combustion is insufficient. For the temperature of structural components, the temperature of the beam and column changes near the fire source lag behind the air temperature. In the overall high-power fire test, considering the spread and development of the fire, the temperature changes of the fire site are more complex. And the temperature rises and displacement changes of the structural components at different positions have corresponding time sequences. Despite the 2 h fire protection of the steel column, the failure of the steel beam led to the overall inward collapse of the portal rigid frame in 32 min. It can be seen that: for the portal frame structures with small structural redundancy, the fire resistance limit of the whole structure depends on the members with small fire resistance limit, and the fire protection design should be considered from the requirements of the overall fire resistance limit of the structure.