Salisbury City celebrated their third successive win and increased the pressure on Wrexham boss Dean Saunders.
Stuart Anderson headed a ninth-minute opener, his first Salisbury goal, from Luke Ruddick's free-kick.
Matt Tubbs made it 2-0 within eight minutes, firing in Darrall Clarke's cross for his ninth goal this season.
Gareth Taylor headed in his seventh goal this season but it was little consolation for a Wrexham team who have won just seven of 31 league games.
Salisbury, who were deducted 10 points after going into administration, now leapfrog Wrexham in the Blue Square Premier League table.
Wrexham manager Dean Saunders said: "In the first-half it was the poorest we have been and to give the goal away as we did, it drives me around the bend. You'd swear we didn't do any set-piece practices. It's a different player every week allowing his man to run free.
"It kicks all of the supporters in the teeth, kicks me in the teeth and kicks the players in the teeth - and then they scored a second goal.
"In the second-half we should have won the game as we missed about five or six chances, including two or three easy tap-ins, and we couldn't get the ball into the net.
"We looked a bit frozen today in the first-half as if we were all frightened to have the ball.
"And we don't work all week in training to smack the ball on Gareth Taylor's head every time we have the ball, which is also driving me around the bend."
Salisbury manager Tommy Widdrington told BBC Wiltshire:
"It was a fantastic result for us, I thought we did the hard work in the first half.
"For a group of lads so young, I think the average age of my back four was probably 18, I just thought they put their tin hats on and dug in in the second half.
"The lads put themselves on the line and I couldn't be any happier than I am."
Wrexham: Maxwell, Obeng, Assoumani, Sinclair, Neil Taylor, Jones, Taboubi (McCluskey 60), Smith (Fleming 46), Sakho (Cieslewicz 60), Gareth Taylor, Marc Williams. Subs Not Used: Mike Williams, Baynes.
Booked: Neil Taylor, Sakho, Gareth Taylor, Assoumani, Fleming.
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