在英国大学读完本科加研究生4年以后申请美国研究生还需要托福成绩么

需要。
如果之前的雅思成绩没有过期，你跟学校院系小蜜问一下
一般美国是需要托福成绩。但也许说不定可以特例。

如果你在英国拿了本科学位的话，绝大多数美国大学都会给他免托福成绩的。
专家提供：美桥咨询

现在有很多美国学校都承认雅思成绩了，具体看你申请的学校，可以打电话，发邮件去问问。

一般来说是不需要的，题主在英国读本科加研究生共4年，很多学校规定的是在英语教学的学校呆满两年以上就可以免托福或者雅思。
例如康奈尔大学的豁免要求：
The English language proficiency requirement may be waived if the applicant meets at least one of these criteria:
1. is a citizen or permanent resident of the United States, or a citizen of the United Kingdom, Ireland, Australia, New Zealand or Canada (except Quebec). Applicants who are citizens of India, Pakistan, the Philippines, Hong Kong, Singapore, etc. are not exempt from the requirement.
2. at the time you enroll at Cornell, you will have studied in full-time status for at least two academic years within the last five years in the United States, the United Kingdom, Ireland, Australia, or New Zealand, or with English language instruction in Canada or South Africa. Even if English was the language of instruction at your school, if you did not study in one of these countries you are not exempt from the requirement. You must submit a transcript that shows you attended college in one of the approved locations, and that your academic program was at least two years in length.
当然不同的学校的要求会不太一样，少部分学校可以在英语为母语的国家取得本科或者研究生学位后免语言。
例如乔治华盛顿大学的豁免要求：
Exceptions to this policy may be granted to applicants who:
1. Hold a bachelor’s, master’s or doctoral degree from an institution in which English is the language of instruction and the official language of the country in which the university is located, or
2. Hold a bachelor's, master's, or doctoral degree from an institution accredited by a U.S. regional accrediting agency (PDF).
祝题主好运！