Spiral vortex flow in the counter-rotating Couette-Taylor system with a large aspect ratio and an intermediate gap has been investigated using Particle Image Velocimetry (PIV). From data of velocity components, we have determined nonlinear properties (anharmonicity, mirror symmetry, axial and radial flow rates) of spiral vortices and compared them to those of Taylor vortices. The velocity field around a spatio-temporal defect has been measured. There is a good agreement between these experimental results with available results from numerical simulations.