I was running on the freeway (65 mph) then my 99 Sub just die.
I had check all the fuses, the fuel pump relay and everything seems to be ok. The fuel pump make the working noise when I turn the key to the On position. I had changed the fuel pump today to see if there is a problem on it but still not starting. But when I put some starting fluid on the intake (is the 5.7 vortex) the engine starts and works for couple seconds.
Where could be the problem?

See if you got fuel pressure at the test port. It is on top of the intake by the firewall. You should have 50-60 psi. Fuel filter?

It may be the theft deterrent system, we had similar problem on our 99 Tahoe.