The intention of this project is to describe the state of the art in the field of optical fibers that are used to the direct measurements of biomedical application by locating the optical probe either in contact with the human skin or inside the human body.The fiber optic techniques are widely used in medicine for sensing or measuring blood oxygen saturation, blood PH, blood gases, respiration monitoring, gastroenterology, ophthalmology, dermatology, dentistry as well as over all assessment of blood flow measurement.An important field of application is the measurement of blood flow velocity inside the artery or vein, the proposed technique has been designed to optically perform the measurement of the blood cell velocity directly inside the vessel by using a small optical fiber (few micrometer diameters).The laser Doppler shift technique has become recently one of the cutting edge techniques after many years of development and research while still ongoing, this project was initiated to design and construct a laser Doppler velocimetry with use in laboratory setup with the aid of standard He-Ne laser, This device depends on theory of the Doppler shift.The analysis and a mathematical model of the laser modulation by using MATLAB Package (version 6.5) is used to represent the measuring velocity of blood for five vessel for different radius and calculate the effect of the change in angel of laser application , in addition another part of this theses is experimental work to evaluate the velocity of blood flow.