Why has china got there own new year?

You seem to divide the whole population of earth between "Everyone" and "China". It's wrong.

There are several cultures and they have their several different calenders. It's just that for the sake of convenience all have chosen to follow the Gregorian Calendar. And there is a new year day according to each of them.

Here's a list of different calender systems being used in different cultures and religions
http://en.wikipedia.org/wiki/List_of_calendar_systems#In_current_use

Many cultures have different new years based on historical calculations.

There is a Jewish New Year; Islamic New Year; Chinese New Year; Tibetan New Year, etc. This site lists some of the better known new year celebrations and how they came to be:

http://www.101lifestyle.com/festivals/new_year/different.html

Good luck!

Many civilisations have their own set of calendaring systems depending on their cultural, religious evolutions etc. There are many different calendar so each has their own new year and not only China has a different one.

The so call common calendar we all are familiar and using today is the Gregorian calendar only becomes defacto standard in recent time either in 19th or 20th century so that everyone has a common reference for trades, communications etc. As to why Gregorian and not others become the de facto standard you must thank the European for colonising the world in the last few centuries. But even the Europeans are not using the same calendar they used thousand of years ago.

But many countries are still referncing their own calendars for various reasons eg. agricultural, cultural, religious etc.

After world war 2 the United Nations proposed to establish a new calendar but postponed the issue after a veto from the USA.

Suggest you start reading from here:

http://en.wikipedia.org/wiki/Calendar
http://en.wikipedia.org/wiki/Calendar_reform

As far as I know, not only China but also some west countries have their own new year, such as Russia.

they are celebrating the year of a certain animal and it has to do with a fortune calender thing i took a whole class on china

because the traditional chinese calendar was lunar (i think) meaning that it came at a different time of year to the rest of us

Because the Chinese (as well as Korean and Vietnamese) go by the lunar calendar.

because foreigners brought their own New Year (1st of Jan) in spite of the fact the whole China is living by their own calendar...
thus there are two New Years now...

the Chinese use a lunar solar calender they use the 12 month system like we do but they always start a month with a new moon and their new year starts with the first new moon after our new year

In early parts of history the whole Chinese section of the world was isolated from the rest of the world and therefore had a different culture than the rest of the world. For example, their chinese characters are nothing like how the rest of the world writes. they isolated themselves on pupose. For what reason I wouldn't know. Mybe so they wouldn't be effected by the rest of the worlds trials and tribulations.