The strength and behavior of composite slabs are mainly governed by the longitudinal shear connection between profiled steel decking and concrete. The composite slab is an orthotropic plate element that the design resistance of composite slabs especially for the longitudinal shear resistance can`t be derived directly from simple calculation in current code of standards around the world. Up to this moment, the most reliable approach in standards for evaluation and prediction of these parameters is traditional performance tests. However, the present test configuration of slab tests does not reflect the realistic performance of load-carrying capacity and behavior of composite slabs. On the other side, some of unfavorable phenomenon was influenced the strength that seldom occurred on site condition and normal practical usage. To investigate the actual performance of composite slabs, eighteen simply supported onespan test specimens were prepared with shorter and longer shear spans. Three different configurations of specimens namely, single width slab, double width slab and side lapping slab in one panel width have been adopted in simply supported slabs. The same geometry and grade of re-entrance profiled steel decking without end anchorage were assumed in this study. The test program was prepared in accordance with the requirement of Eurocode 4 which is currently in force in Macau. In this experimental study, the structural performance of composite slabs such as maximum applied load, displacement, end slips and strain of concrete and profiled steel decking as well as failure mode of the full scale slabs are investigated and presented among three different configurations of test specimens. A comprehensive parametric and results analysis have been carried out to investigate the behavior and performance of composite slabs among the specimens. The test results in ultimate and serviceability limit state have been recorded and studied in this paper. The parameters of mechanical interlock (m) and friction (k) were investigated from the three series of specimens. The longitudinal shear bond resistance between profiled steel decking and concrete was determined by two methods: by m-k and partial shear connection method (PSC). The difference between two methods from all specimens varies from 4.6% to 31.9%. A considerable increase occurs on the resistance of slabs for namely, side lapping slab specimens compared with single width slab specimens or double width slab specimens. On the other side, the dramatic increase on ultimate resistance of 121% and 158% for specimens of double width slab was found compared with the test results of single width specimens. It is shown that the slabs with short shear span have a higher ultimate load resistance and shear bond resistance than that of the composite slabs with longer shear span. The edge web curling in the specimens of single width panel and double width panels occurred in the slabs with short shear span during the experiments. The edge deflection of slabs was greater than the center deflection at mid span section. These results revealed that the shortcomings in present test configurations that need to consider and improve in future experiment in order to evaluate the actual performance of composite slabs. Based on the test results, a proposed calculation for predicting the ultimate resistance of wide slabs in this paper is in good agreement with the performance test results of full scale specimens.