I found LSAT CRs to be of 700 level in GMAT

But the LSAT RCs from the earlier tests either seem easy or the questions are mostly based on the passage ( Most of them are specific- according to the passage - kind of questions ). It does not help you tackle the inference, author's intent kind of questions which is more frequent in GMAT

I would definitely disagree with this:

It does not help you tackle the inference, author's intent kind of questions which is more frequent in GMAT

LSAT RC, especially from preptests numbered 30 and higher have a very high concentration of inference, logic function, parallelism questions etc. I teach both tests, and I can tell you that the hardest LSAT RC is definitely harder than the hardest GMAT RC.

That said, there are important differences between the two tests. A tough GMAT RC passage is likely to be quite technical while the wording is often quite straightforward. Conversely, a tough LSAT RC typically isn't highly technical but will be highly abstract with very dense and sophisticated academic prose.

Can working on LSAT RC help you?

Most likely, yes.

But I still think it is better to practice on official GMAT questions.

Can GRE passages help you? I've seen some good ones. But I don't teach GRE on a regular basis, so I will refrain from commenting about that other than to reiterate that your interests are best served practicing with GMAT materials.

duongthang wrote:I wish to practice reading more. Can I use GRE and LSAT passages for gmat practice. I see that LSAT passages are more of law and different from gmat passages.

or I should practice only gmat passages.

Topic doesn't matter. The thing which matters is "ability to see the raltionship between idea, inference and assumption in certain cases where things are not said explicitly as asked". People freak out when they see terms like "defendent" or "plaintiff" or "adjudication" etc and start thinking that this has to do something with Juris Dotor which has nothing to do.
LSAT is best for RC I find some LSAT passage more easy than GMAT. The reason I find is LSAT complexity is about length and interpreation of something said in one paragraph of passage with its impact in other paragraph of same passage. But in GMAT test maker try to notoriously change the expression through replacing various sentences and making it more complex not in depth but through haphazard referencing and putting so many adjectives with noun.

GMAT would say: The robert, whose mother still believe in colonial age, the age which was finished in early 18th century, the century which is made on 100 years, those 100 years can carry a lot of change within the socio-economic environment of society as evidenced in scottish society in throughout early 18th century and despite of all that thoughts of his mother, robert will not agre with his mother.