Do i need a tourist visa for visit UK if i have US "green card"?

It depends on your citizenship. Your Green Card does not count for the United Kingdom. If you are not a citizen of a European Union country or of Andorra, Antigua & Barbuda, Argentina, Australia, Bahamas, Barbados, Belize, Botswana, Brazil, Brunei Darussalam, Canada, Chile, Costa Rica, Croatia, Dominica, El Salvador, Grenada, Guatemala, Honduras, Iceland, Israel, Japan, Kiribati, Korea (Republic of), Liechtenstein, Malaysia, Maldives, Marshall Islands, Mexico, Micronesia, Monaco, Namibia, Nauru, New Zealand, Nicaragua, Norway, Palau, Panama, Papua New Guinea, Paraguay, Saint Kitts and Nevis, Saint Vincent and the Grenadines, Samoa, Santa Lucia, San Marino, Seychelles, Singapore, Solomon Islands, South Korea, Switzerland, Timor-Leste, Tonga, Trinidad and Tobago, Tuvalu, USA, Uruguay, Vatican City, Vanuatu you will need a visa.

Citizens of Venezuela are only visa waived if they hold one of the new electronic passports.

To check for sure enter your citizenship, residency and the purpose of travel on the questionnaire on the bottom of the web link.

Source(s):

http://www.ukvisas.gov.uk/en/

Your US green card has absolutely no value or use in the UK or Europe - but just carry it in the back of your wallet because the only time you'll need it is to get back into America on your return home - it means nothing here. You will need a PASSPORT to visit the UK - depending on the nationality of that passport you may or may not require a Visa - an American citizen travelling on an American passport should not need a Visa for a short term stay in the UK - but if you intend to stay for 6 months or more - or work here you will need a Visa.

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