Marriott Corp. announced yesterday that construction will begin within a few months on a multi-million-dollar headquarters complex in Montgomery County, at the intersection of Interstate 270 and Democracy Boulevard.

The restaurant, hotel and airline catering firm, founded in Washington 50 years ago and now based Bethesda, will move about 1,400 personnel to the new headquarters when the building is finished late in 1978.

Located on a 34-acre site, the 537,000-square-foot headquarters will include food research and development laboratories, a national computer facility and a mangement training center.

The buildings's architect is Mills and Petticord/HOK, nationally known for designing such structures as the National Air and Space Museum. Dallas-Ft. Worth International Airport, George Washington University Medical Center and Ralston Purina's headquarters in St. Louis. The Marriott bulding facade will step back on alternate floors while landscaping will include a pond. Parking spaces for 1,000 cars will be provided.

Marriotts main headquarters at 5161 River Rd. has become crowded in recent years as the firm grew to its current annual sales volume of about $1 billion. Some divisions now are based in separate offices in the Bethesda area.

A general contractor for the project has not been selected, the company said, but Meade Palmer of Warrenton is the landscape architect.

Formal groundbreaking ceremonies are scheduled for May, to coincide with founder J. Willard Marriott's opening on a root beer stand on George Avenue NW on May 21, 1927, where the business began. The current headquarters structure is for [WORD ILLEGIBLE] the firm said.