Try to use this code to export the data to excel, may it ll help
public static void DataSetsToExcel(DataSet dataSet, string filepath)
{
    try
    {
        string connString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + filepath + ";Extended Properties=Excel 12.0 Xml;";
        string tablename = "";
        DataTable dt = new DataTable();
        foreach (System.Data.DataTable dataTable in dataSet.Tables)
        {
            dt = dataTable;
            tablename = dataTable.TableName;
            using (OleDbConnection con = new OleDbConnection(connString))
            {
                con.Open();
                StringBuilder strSQL = new StringBuilder();
                strSQL.Append("CREATE TABLE ").Append("[" + tablename + "]");
                strSQL.Append("(");
                for (int i = 0; i < dt.Columns.Count; i++)
                {
                    strSQL.Append("[" + dt.Columns[i].ColumnName + "] text,");
                }
                strSQL = strSQL.Remove(strSQL.Length - 1, 1);
                strSQL.Append(")");
                OleDbCommand cmd = new OleDbCommand(strSQL.ToString(), con);
                cmd.ExecuteNonQuery();
                for (int i = 0; i < dt.Rows.Count; i++)
                {
                    strSQL.Clear();
                    StringBuilder strfield = new StringBuilder();
                    StringBuilder strvalue = new StringBuilder();
                    for (int j = 0; j < dt.Columns.Count; j++)
                    {
                        strfield.Append("[" + dt.Columns[j].ColumnName + "]");
                        strvalue.Append("'" + dt.Rows[i][j].ToString().Replace("'", "''") + "'");
                        if (j != dt.Columns.Count - 1)
                        {
                            strfield.Append(",");
                            strvalue.Append(",");
                        }
                        else
                        {
                        }
                    }
                    if (strvalue.ToString().Contains("<br/>"))
                    {
                        strvalue = strvalue.Replace("<br/>", Environment.NewLine);
                    }
                    cmd.CommandText = strSQL.Append(" insert into [" + tablename + "]( ")
                        .Append(strfield.ToString())
                        .Append(") values (").Append(strvalue).Append(")").ToString();
                    cmd.ExecuteNonQuery();
                }
                con.Close();
            }
        }
    }
    catch (Exception ex)
    {
    }
}