I have installed magento 1.9.1.0, but on backend I can't find a mobile button.
Why magento 1.9.1.0 Remove Admin Panel > mobile? And if I want to make my webapps in the future, how I can't do without mobile?
Make sure that the Mage_XmlConnect module is enabled. I believe it's disabled by default on Magento CE 1.9.1 (equivalent to EE 1.14.1). To check, open app/etc/modules/Mage_XmlConnect.xml and look at the <active></active> tag. If it says false, change it to true.