What's the matter with blurred portraits taken at night with d7000?

This is caused by insufficient ambient light, slow shutter speed and shaking hands. You can try the following solutions:

1. Improve ISO. If your camera has a good high sensitivity effect and can accept noise, then increase ISO to improve the shutter speed;

2. Fill the light with a flash, which is the most direct way to improve the shutter speed, but the flash will destroy the ambient atmosphere and the background will be very dark;

3. Make full use of ambient light, tripod+slow shutter+flash Hou Lian synchronization.