Fire accident is one of the most frequently occurring accidents that could happen to any service structures in unexpected times. It requires a little source to be ignited but takes much more effort and cost to be controlled. In our country, Ethiopia, there were so many fire accidents which damaged many structures. The properties of concrete under normal temperatures are mostly well understood and those properties have been used for the design of concrete structures. However, under extreme temperature, our knowledge of these properties is not well documented and makes it difficult to take into account fire resistance in the design of structures. A repeated and hazardous fire accidents causing loss of valuable human life, failure of structures and the difficult circumstance to make fire accident under control within shorter time, increases an interest in the design of structures for extreme temperature or fire. This paper focused on studying the effect of temperature on concrete strength. Performance of concrete after concrete exposed to extreme temperature is investigated. Performance here indicates the response of concrete subjected to extreme temperature; it includes variation of compressive strength with the reference of stress-strain cure and variation of vertical displacement and load carrying capacity with the reference of load-displacement curve for different temperature and temperature exposure duration. In this paper; concrete grade, temperature and duration of temperature exposure are taken as factor to be considered for concrete strength. Experimental investigation was carried out on cylindrical concrete and plain concrete beam for each concrete grades to compare the compressive strength and load carrying capacity of concrete after it has been exposed to desired temperature. And it has been found that compressive strength of C-15 and C-25 concrete significantly decreases linearly in early temperature and compressive strength of C-40 concrete significantly decreases linearly in later temperature. It has been found that higher concrete grade shows better fire resistance. The rate at which the concrete lost strength for each concrete grade is also investigated.