A reliable understanding of the properties of 3-D braided composites is of primary importance for the successful utilization of these materials. A new method is introduced to study the mechanical performance of braided composite materials using embeddedoptic fiber sensors. Experimental research is performed to devise a method of incorporating the optic fiber into a 3-D braided composite structure. The efficacy of this new testing method is evaluated on two counts. First, the optical performance of the optic fiber is studied before and after incorporation into the 3-D braided composites, as well as after completion of the manufacturing process for the 3-D braided composites, to validate the ability of the optic fiber to survive the manufacturing process. On the other hand, the influence of incorporated optic fiber to the original braided composite is also researched by tension and compression experiments. Second, two kinds ofoptic fiber sensors are co-embedded into 3-D braided composites to evaluate their respective ability to measure internal strain. Experimental results show that multipleoptic fiber sensors can be co-braided into the 3-D braided composites to determine its internal strain which is difficult to be fulfilled by other current existing methods.