I'd like set the thickness of edge in dot file, but could not find the corresponding attribute, anyone know that ? Thanks
You are probably looking for penwidth:
Specifies the width of the pen, in points, used to draw lines and curves, including the boundaries of edges and clusters. The value is inherited by subclusters. It has no effect on text.
Previous to 31 January 2008, the effect of penwidth=W was achieved by including setlinewidth(W) as part of a style specification. If both are used, penwidth will be used.