hi,anyone know how to extract datas like velocity and mixture fractions from fluent in order to plot them on graphs using like matlab program?

Try:

PLOT .. XYplot select what you want to save (velocity for example)then you could save the rezults in a file with WRITE and use them in Matlab.

I hope this could help, but it is strongly recomanded that you read the help, especially the Postprocessing chapter.

The best way is writing profile for this purpose just go to file menu>write>profile then select the surface you want to view the data on then select the velocity or pressure or anything else from values menu.