BSTR bstrstr;//这是你要转换的BSTR变量
LPCOLESTR szFromBSTR;
szFromBSTR=bstrstr;
int nLen;
nLen=WideCharToMultiByte(CP_ACP,0,szFromBSTR,-1,NULL,NULL,NULL,NULL)
LPSTR szNewStdString;//这是转换的结果变量
szNewStdString=(char)malloc(nLen);
WideCharToMultiByte(CP_ACP,0,szFromBSTR,-1,szNewStrString,nLen,NULL,NULL);
//就这样.