1.In ssh service agent (controlled computer)，find /etc/ssh/sshd_config，make sure [ X11Forwarding yes ],note no [ # ] in front of [ X11Forwarding ]，and then :

cd /etc/init.d
./ssh restart

2.In local agent，find /etc/ssh/ssh_config，make sure

ForwardAgent yes
ForwardX11 yes
ForwardX11Trusted yes

3.Next open terminate，assume ubuntu local agent ip is 1.1.1.1，ssh service agent ip is 2.2.2.2 .Connect to controlled computer by

xhost +2.2.2.2
ssh -X username@2.2.2.2   | or ssh -Y username@2.2.2.2  
export DISPLAY="127.0.0.1:10.0"

Test : 

xclock

ssh GUI in local Ubuntu14.04