要提前创建工作表，需要将创建的工作表添加到sheets字典中：

writer.sheets['Validation'] = worksheet
使用您的原始代码：

# Creating Excel Writer Object from Pandas  
writer = pd.ExcelWriter('test.xlsx',engine='xlsxwriter')   
workbook=writer.book
worksheet=workbook.add_worksheet('Validation')
writer.sheets['Validation'] = worksheet
df.to_excel(writer,sheet_name='Validation',startrow=0 , startcol=0)   
another_df.to_excel(writer,sheet_name='Validation',startrow=20, startcol=0)

说明

如果我们看一下pandas函数to_excel，它使用了作者的write_cells函数：

excel_writer.write_cells(formatted_cells, sheet_name, startrow=startrow, startcol=startcol)

所以看看xlsxwriter的write_cells函数：

def write_cells(self, cells, sheet_name=None, startrow=0, startcol=0):
    # Write the frame cells using xlsxwriter.
    sheet_name = self._get_sheet_name(sheet_name)
    if sheet_name in self.sheets:
        wks = self.sheets[sheet_name]
    else:
        wks = self.book.add_worksheet(sheet_name)
        self.sheets[sheet_name] = wks

在这里我们可以看到，它在self.sheets中检查sheet_name，因此也需要将其添加到self.sheets中。

用户3817518：“请分享是否有其他方法可以使用内置的www.example.com _excel功能将许多数据框放入exceldf.to！！”
以下是我的尝试：
简单的方法把很多 Dataframe 放在一个工作表或多个标签。让我知道如果这工作！
--要进行测试，只需运行示例 Dataframe 以及第二和第三部分代码。

Dataframe 示例

import pandas as pd
import numpy as np

# Sample dataframes    
randn = np.random.randn
df = pd.DataFrame(randn(15, 20))
df1 = pd.DataFrame(randn(10, 5))
df2 = pd.DataFrame(randn(5, 10))

将多个数据框放入一个xlsx表中

# funtion
def multiple_dfs(df_list, sheets, file_name, spaces):
    writer = pd.ExcelWriter(file_name,engine='xlsxwriter')   
    row = 0
    for dataframe in df_list:
        dataframe.to_excel(writer,sheet_name=sheets,startrow=row , startcol=0)   
        row = row + len(dataframe.index) + spaces + 1
    writer.save()

# list of dataframes
dfs = [df,df1,df2]

# run function
multiple_dfs(dfs, 'Validation', 'test1.xlsx', 1)

将多个数据框放在不同的标签/表单中

# function
def dfs_tabs(df_list, sheet_list, file_name):
    writer = pd.ExcelWriter(file_name,engine='xlsxwriter')   
    for dataframe, sheet in zip(df_list, sheet_list):
        dataframe.to_excel(writer, sheet_name=sheet, startrow=0 , startcol=0)   
    writer.save()

# list of dataframes and sheet names
dfs = [df, df1, df2]
sheets = ['df','df1','df2']    

# run function
dfs_tabs(dfs, sheets, 'multi-test.xlsx')

阿德里安的回答可以简化如下
writer = pd.ExcelWriter('test.xlsx',engine='xlsxwriter') df.to_excel(writer,sheet_name='Validation',startrow=0 , startcol=0) another_df.to_excel(writer,sheet_name='Validation',startrow=20, startcol=0)
适用于pandas 0.25.3和python 3.7.6

使用with-您不必显式调用writer.save()或writer.close()。
此外，如果您使用workbook=writer.book，它会自动管理workbook.close()。
（其他答案忘了这样做，而这种情况相当经常发生，因为我们是人;）

import pandas as pd 

df = pd.DataFrame(data={'col1':[9,3,4,5,1,1,1,1], 'col2':[6,7,8,9,5,5,5,5]}) 
df2 = pd.DataFrame(data={'col1':[25,35,45,55,65,75], 'col2':[61,71,81,91,21,31]}) 

with pd.ExcelWriter('test.xlsx', engine='xlsxwriter') as writer:
    df.to_excel(writer, sheet_name='testSheetJ', startrow=1, startcol=0)
    df2.to_excel(writer, sheet_name='testSheetJ', startrow=1+len(df)+3, startcol=0)

结果：

我更倾向于先连接 Dataframe ，然后将 Dataframe 转换为Excel格式。要将两个 Dataframe 并排放在一起（而不是一个在另一个上面），请执行以下操作：

writer = pd.ExcelWriter('test.xlsx',engine='xlsxwriter')   # Creating Excel Writer Object from Pandas  
workbook=writer.book
df.to_excel(writer,sheet_name='Validation',startrow=0 , startcol=0)   
new_df = pd.concat([df, another_df], axis=1)
new_df.to_excel(writer,sheet_name='Validation',startrow=0 , startcol=0)

将多个数据框写入一张excel表

# Position the dataframes in the worksheet.
df1.to_excel(writer, sheet_name='Sheet1')  # Default position, cell A1.
df2.to_excel(writer, sheet_name='Sheet1', startcol=3)
df3.to_excel(writer, sheet_name='Sheet1', startrow=6)

# Write the dataframe without the header and index.
df4.to_excel(writer, sheet_name='Sheet1',startrow=7, startcol=4, header=False, index=False)