International Harvester Co. announced a realignment of its management structure yesterday to fit the drastic reduction in the debt-ridden company's size announced three weeks ago.

The juggling of corporate duties, which involves the reassignment of executives from the executive-vice-president level and down, is the second in about a year for Harvester. In the past few months, the troubled company also has replaced its chairman and president and lost about a half dozen other top executives.

The changes reflect the company's intention, announced on July 29, to get out of the construction-equipment business and to scale down dramatically its truck and farm tractor operations. It also creates a structure to oversee the divestiture of businesses and facilities that Harvester said it would shed under the plan.

"This is just getting the players in place for our July 29 plan," a Harvester spokesman said.

As part of the reorganization, Harvester had said it would lay off 1,200 of its 13,000 white-collar employes at its Chicago headquarters and elsewhere by Sept. 30. The spokesman said yesterday that the company still has not decided exactly which employes would be let go under that plan.

The new organizational chart in a way reverses a structure put into place last year that concentrated all of Harvester's manufacturing operations under an executive vice president for manufacturing, while putting truck operations under another executive vice president and agricultural and construction equipment under a third executive vice president. Formerly, each Harvester division was separate and was headed by an officer carrying the title of president.

Under the new arrangement, the post of executive vice president-manufacturing has been eliminated, apparently in keeping with Harvester's plans to concentrate its North American manufacturing operations in a handful of plants. J. Patrick Kaine, who had been executive vice president of the truck group, will get the new position of executive vice president for trucks and agricultural equipment, in charge of most phases of production and sales of those products.

Harvester also will form an administrative services group to oversee information systems, parts distribution, material management, quality assurance and engine production. The company also said it would close some of its scientific and technical laboratories to reduce costs further.