In this paper, the spreading of three-dimensional, turbulent and unsteady inclined turbidity currents has been investigated. The experimental results were normalized in the form of non-dimensional plots and then a theoretical model was developed. The current width, b, and the relative situation of the tip of the nose of turbidity current, x, are normalized with respect to the buoyancy length scale and related time t is normalized with respect to the buoyancy time scale. Results show that the non-dimensional current width vs non-dimensional distance and non-dimensional time, , two regimes and are distinguished. This indicates that in these two regimes, the amount and type of the balanced forces are different. In regime , the rate of lateral growth is less than regime , while the current width in and regimes, respectively are proportional to and . In the plots of the non-dimensional current length vs. non-dimensional time, three regimes , and are distinguished. In regime , the rate of longitudinal growth is more than other regimes while regime is less. The current length in and regimes, respectively are proportional to and , approximately in regime , is proportional to