Hi Youfei,
Thanks for using Syncfusion products.
We suggest you to use “ColumnWidthMode” property of chart control to specifies the width drawing mode for the columns in a column chart.
You can find more information about these properties in the online documentation link from below.
http://help.syncfusion.com/ug_91/User%20Interface/Windows%20Forms/Chart/Documents/4515columnwidthmode.htmPlease let us know if it helps.
Regards,
Vijayabharathi