The invention provides an optical fiber loss measuring system which comprises a laser signal generator and an optical fiber output detecting component. The laser signal generator is used for generating laser and injecting the laser into fiber cores of detected optical fibers. The optical fiber output detecting component is used for separating a fiber core light field and a wrapping layer light field of the fiber cores of the detected optical fibers, and fiber core loss and wrapping layer loss of the detected optical fibers are measured according to the fiber core light field and the wrapping layer light field obtained by separating. The optical fiber loss measuring system can measure the fiber core light field and the wrapping layer light field of the detected optical fibers and can improve the accuracy of measuring.