The project conducated and presented in this paper is regarding experimental work on air compressors which emphasis is given to reciprocating aircompressor. The case selected for the project is CUSSONS P9050 TWO STAGE RECIPROCATING AIR COMPRESSOR TEST SET which is available in the Thermodynamic Laboratory, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia.Description regarding the working principle of a single and double stagereciprocating air compressor is given in which, progress has taken place to identify and rectify the air compressor to obtain the rquired working condition. Two experimental work on this reciprocating air compressor have been introduced. The first experiment is about the effect of delivery pressure on the performanmce of a single stage reciprocating air compressor test set. The second is about the effect of delicery pressure on the peerformance of a double stage reciprocating air compressor test set with three different working condition. Thus, the results of both experiments are able to conclude the efficiency of an air compressor on different stages with specified workingconditions. Based on this, the procedure for conducting these experiments have been outlined. Finally, a simple computer programme with a sample output is povided together a complete procedures in conducting the above mentioned experiments is given.