@elanchezhiyan,
Whisker length depends on multiple factors like dataPointWidth, dataPointMaxWidth, axis range, etc. In your case, the whisker length gets limited because you are setting x-axis range(I noticed you are setting axisX minimum and maximum). Removing these properties should work fine.
However, if you would like to override this behavior, you can set whiskerLength as well as increase the default dataPointWidth.
Please check this JSFiddle for a working example.
—
Thangaraj Raman
Team CanvasJS