TypeScript不知道它不知道什么.它不知道在任何给定的updateAxiosOptionsHeaders运行中key将是什么，所以它 Select 最严格的可能解释.当然，有很多不同的方法来解决这个问题，但是如果你想保持类型不变，你可以在函数中解决它:

type ApiHeaders = {
  Accept: string;
  'Content-Type': string;
  IsRequireAdmin: 'true' | 'false';
  Authorization?: string;
  BarCode?: string;
  DomainName?: string;
};

interface AxiosOptions {
  params?: any;
  data?: any;
  headers: ApiHeaders;
}

const axiosOptions: AxiosOptions = {
  headers: {
    Accept: 'application/json',
    'Content-Type': 'application/json',
    IsRequireAdmin: 'false'
  }
};

const updateAxiosOptionsHeaders = (newApiHeaders: Partial<ApiHeaders>): void => {
  let key: keyof Partial<ApiHeaders>;
  for (key in newApiHeaders) {
    if (key === 'IsRequireAdmin') {
        // Note the default value if one isn't provided in newApiHeaders for some reason
        axiosOptions.headers.IsRequireAdmin = newApiHeaders.IsRequireAdmin ?? 'false';
    } else {
        // ditto here
        axiosOptions.headers[key] = newApiHeaders[key] ?? '';
    } 
  }
};
const token: string = 'my_token';
const barCode: string = 'my_bar_code';
const domainName: string = 'www.mydomain.com';

const newApiHeaders: Partial<ApiHeaders> = {
  'IsRequireAdmin': 'true',
  'Authorization': `Bearer ${token}`,
  'BarCode': barCode,
  'DomainName': `DATA\\${domainName}`
  };

updateAxiosOptionsHeaders(newApiHeaders);

查看更改部分的注释；您需要决定合理的缺省值.