Hi Nguyen Duy Hung,
Thanks for your interest in Syncfusion Product.
I have opened one sample excel file. In sample file, in active sheet, Active row index is 6. I tried to insert the row at index 1. Row is inserted at index 1 correctly and no deletion of rows occurs.I have attached the sample file. Please try this at your side and let us know whether this helps you.
Thanks,
Manikandan.M
Sample_c984e17f.rar