i am installing centos7 but why i cant log in, but i have a problem..

You don't provide enough information. Did you do a full GUI install, or just a command-line server install? Do you get to a login screen or window? If so, after the first part of the installation and it boots for the first time, it should ask for a user ID and password. Did you get that? Also, when installed, it should have asked for a root user password. Did you set that?

yes i am installed full GUI, and log in screen appear,first time boot and ask me give user name and pasword.
but when i am giving user name password option apeera but i dont enter password because key board dont show any responce and my enter password is not enterd,after 2 min message appera you cant log in..
CentOs Linux 7 (core)
Kernel 3.10.0-123 .x86-64 on an x86_64
asdi login:_
when i am giving log in name asad and enter then i have not acess to enter password..

-bash : q1w1e1r1t1y1u1i1: command not found
this error is occured. my password is q1w1e1r1t1y1u1i1

This may be a keyboard connectivity issue. Is it USB, or other? Have you tried to install CentOS 6.x? Does it behave similarly? CentOS 7.x is very new, so there may be some hardware issues that the team needs to know about. If 6.x installs OK, then report this to the CentOS user forums.