//dgvVisitor 是DataGridView的名称
dgvVisitor.RowsDefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleCenter;
 //单元格居中显示
    private void dgvVisitor_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
  {
      e.CellStyle.Alignment = DataGridViewContentAlignment.MiddleCenter;
  }

//设置第3行第3列的单元格内容居中显示
dgvVisitor.Rows[2].Cells[2].Style.Alignment = DataGridViewContentAlignment.MiddleCenter