As the field of Micro-Fluidic-Systems (MFS) is still at it early stage of development, only some simple optical devices such as liquid waveguide and liquid optical switches have been reported. The lack of in-depth analysis makes some novel photonic phenomena unexplained and uninvestigated in MFS. Solutions to these problems require a lot of imagination and ingenuity. In this paper, dynamic liquid optical splitters and interferometers have been demonstrated by diffusion according to flow rates are reported. In the case of the Y splitters, light from a single source can be split into two directions with angle-controlled dynamic. To the interferometers, light from a single source can be split and then combined to interference. The lengths of the interferometers can be controlled from via control of diffusion coefficient and flow rate. It implies that the Micro-Photonic-Fluidic –Systems may establish a new branches to MFS and has potential applications in biological, chemical and medical solution detectors.