I have a website on Travel and its back links is 100 and i want to increase its back links.
Can anyone tell me please how to improve Back links.
I always try to emphasize the importance of great content on ANY site, before it needs to get links. You need to create content that other people want to link to, and promote it accordingly.
Since you have a travel site, you can write a link bait called "100 Things You Should Not Do While On Vacation" or something similar to this. Articles like this (if properly written and minimally promoted) tend to attract a lot of links. Sure, it might take you a while to write a great, helpful, funny article like this, but it will be well worth it.
Another thing you can do is contact bloggers in your niche (bloggers who like to write about different countries, traveling abroad etc.) and offer them something in return of link. Nothing big, a T-shirt might work. And there you go - you just got relevant, quality links
You can also submit your site to travel directories. I'm not familiar with your niche, but believe that there are quite a number of them worth your time.