Hello friends...Why google crawl my website delay? The last crawled was before 30 days, please suggest some authentic solution.

There are a couple of possible reasons why Google is slow when spidering your site.

Your site doesn't have enough authority.
Technical reasons for slow crawling.
your site is too slow.
Too many errors on your site
You have too many URLs
Your Server is slow.

Too Many URL's On Your Website
A Great Number of Errors in Your Website
Slow Server
High Resolution Images take a Long Loading Time

1. The possibility is it should be used when your website has a number of pages and is a big size website. Crawl-delay can be used in social bookmarking sites, sites like twitter, facebook etc. which are very frequently updated.
2. possibility is may be your site is under sandbox effect.
3. your site is too slow.
4. Too many errors on your site

There are multiple reasons for slow indexing of webpages. But,some of them are major ones. Like if you haven't added a XML sitemap in the website, have XML sitemap but not submitted in the Google webmaster tool, pages are redirecting from one location to another, pages have loops in between them.

There are a couple of possible reasons why Google is slow when spidering your site.

Your site doesn't have enough authority.
Technical reasons for slow crawling.
your site is too slow.
Too many errors on your site
You have too many URLs
Your Server is slow.

Following are the reasons due to which your website is slowly indexed by Google :-

Too Many URL's On Your Website
A Great Number of Errors in Your Website
Slow Server
High Resolution Images take a Long Loading Time