Hello,
Here is my code to get data format of X-Axis

ExcelAxis xAxis = excelChart.easy_getCategoryXAxis();
String dataFormat = xAxis.getNumberFormat();
It then return General, but the expected value is mmm-yy. The chart contained in a spreadsheet that was created with Ms Excel 2003. I am using EasyXLS Reader for java, version 6.1. Attached screenshot was the chart that i want to load.

Please give me some advice on getting correct X-Axis data format.
Thanks in advance.
The chart screenshot:

http://www.flickr.com/photos/tckhanh/2067784840/

Most probably the Linked To Source property is set for the axis. See ExcelAxis.IsNumberFormatLinked() value.
You shoud try to uncheck this option in the xls file that you are reading and try to set the number format for the axis.

Thanks Daniela,
I turned off the "Link To Source" option, but no helps.
Is there another way?

I tried to uncheck the "Linked To Source" option myself and it worked. Do this in your xls document using Microsoft Excel, not in your EasyXLS code. That should solve your problem.