-Yes, he can abandon his green card and apply for the B-2 visa at the same time or later. I have advised more than 10 people did that and they all got the B-2 visa successfully.
关键我母亲一直保持绿卡,签证官会相信父亲没有移民倾向吗?
-It should be fine.
另外如果要办407同时申请签证,必须去广州领事馆还是可以在居住地所属的成都领事馆?
-Any one of the US Consulates is OK. 成都领事馆 is fine.
最后一问,如果无法办理签证,一定要从新办绿卡,我父亲这种情况可以自己办理吗,还是需要专业律师协助?
-It is simple process, and I don't think you need a lawyer. But your father has to abandon the green card first, then you file I-130 to sponsor him to apply for the immigrant visa later. He can abandon his green card by mail or in person. Read this link:
https://china.usembassy-china.org.cn/visas/immigrant-visas/us-citizenship-immigration-services-uscis/abandonment-status-form-407/
谢谢!