要使用Bloomberg API来获取历史指数成员，您需要安装blpapi库和python的pandas库。

以下是一个使用Python的示例代码：

import blpapi
import pandas as pd

def get_index_members(symbol, start_date, end_date):
    # 创建Bloomberg session
    sessionOptions = blpapi.SessionOptions()
    sessionOptions.setServerHost("localhost")
    sessionOptions.setServerPort(8194)
    session = blpapi.Session(sessionOptions)
    session.start()

    # 创建请求
    refDataService = session.getService("//blp/refdata")
    request = refDataService.createRequest("HistoricalIndexCompositionRequest")
    request.set("index", symbol)
    request.set("startDate", start_date)
    request.set("endDate", end_date)

    # 发送请求并等待响应
    session.sendRequest(request)
    while True:
        ev = session.nextEvent(500)
        if ev.eventType() == blpapi.Event.RESPONSE or ev.eventType() == blpapi.Event.PARTIAL_RESPONSE:
            break

    # 处理响应
    members = []
    for msg in ev:
        securityData = msg.getElement("securityData")
        fieldDataArray = securityData.getElement("fieldData")
        for i in range(fieldDataArray.numValues()):
            member = fieldDataArray.getValue(i).getElementAsString("Member Ticker and Exchange Code")
            members.append(member)

    # 停止会话并返回成员列表
    session.stop()
    return members

# 示例用法
symbol = "SPX Index"
start_date = "20210101"
end_date = "20211231"
members = get_index_members(symbol, start_date, end_date)
df = pd.DataFrame(members, columns=["Member"])
print(df.head())

请注意，这只是一个简单的示例，您需要设置正确的Bloomberg服务器主机和端口，并且需要相应的订阅权限才能成功获取历史指数成员数据。另外，您可能需要根据您的具体需求进行适当的修改。