Earlier in the afternoon, France took the bronze for the second successive year following a 67-57 win over Australia.
The USA won the past two championships but had been knocked out by France from the quarter-final round earlier in the week. Argentina then beat France from the semi-final.
In the last match, the Spaniards scored first and never relinquished the lead.
They depended upon exceptional defense and rebounding to snuff out the offensive danger of 2004 Olympic champions Argentina.
Point guard Ricky Rubio racked up 20 points and three assists.
Marc Gasol and Willy Hernangomez swatted three shots every as Spain pulled 47 rebounds, 20 over Argentina, en route to a comprehensive victory.
The 32 team championship has been hosted in China.