Hello Ivy:

 Your English is very good!   I think you can be very confident of your ability to make great progress and Lisa thinks so too.---Warm Regards,  Bruce

2013.2.16

It's so too late...almost 6 o'clock (in the morning?). I don't want to sleep, so I found italki and decided to write something. So far Well,italki seems is very useful for to me to learning English, so I will use it often. I know my English is really bad so poor;I want to improve it my English here. Since you already said "my English", it is best to use a pronoun to refer to it again.

You can say that your English is poor, but we usually say "bad" over "poor". It's just my preference, so feel free to say whichever you want.  

2013.2.16

It's too late...almost 6 o'clock. but I don't want to sleep,so I found italki and write wrote (should be past tense to agree with 'found) something.Well,italki is very useful to me to learn English,so I will use it often.I know my English is so poor......I want to improve my English here.

Use conjunctions to join related clauses, otherwise the sentence structure (as someone comments) is too simple ...  You did so, nicely, with 'so' that's really good.  After punctuation leave a space, and after full stop usually two spaces.

Suggestion:

It's late...nearly 6 o'clock. I don't want to sleep.

I found italki and I thought I should write something. 

My English is poor and I find italki to be very helpful to learn and improve my English, so I will use it often.

Your English is good, sometimes beware of how you structure your sentence.

Otherwise keep up the good work ^^