The Howard County Zoning Board rejected yesterday the Marriott Corporation's proposal to build a $75 million amusement park in the county, handling the giant conglomerate yet another major setback in its persistent five-year effort to build a theme park somewhere in the Washington area.

The zoning board's decision, based on environmental traffic, and esthetic grounds, left Marriott officials "disappointed." but they vowed to continue their search for a suitable 500-acre site in one of the jurisdictions surrounding Washington.

According to Marriott's attorney, Stephen A. West, the company has "definite plans" to build a theme park in the metropolitan area. He said the company has looked at possible sites in Prince George's County and in other areas, but he declined to elaborate.

In March a Marriott proposal to build its entertainment park near Manassas in Prince William County was tied up by court challenges from local citizen groups. Five years ago, company plans to build the park in another part of Howard County were also rejected.

"The site location . . . " proposed by Marriott was "seriously substandard (and) deficient," said Lloyd G. Knowles, chairman of the zoning board, at a press conference yesterday.

Knowles criticized the plans for the park, proposed for a location between Rte. 1-95 and Rte. 1 near Columbia as being "lacking" in plans for anticipated traffic congestion and air pollution.

Because there is no direct acces to the site from 1-95, the major highway in the area, the smaller subsidiary road leading to the proposed park entrance would be clogged with traffic, Knowles said.

The proposed entrance to the giant park would have been directly across Rte.1 from the Maryland Wholesale Food Market. "Numerous and frequent accidents" involving passenger cars and produce trucks were feared if the park were built there, according to a source to the zoning board.

"Our job is not to do the work of those proposing" the amusement park in such areas of traffic flow and pollution, but only to weigh whether the proposal fits the board's published desire for "orderly and controlled growth" within the county, Knowles said.

Knowles and the other three members of the zoning board also make up the elected Howard County Council. Each of the four campaigned for office three years ago in a platform calling for slow, controlled growth for the area. Knowles noted.

The decision stemmed partly from "an image problem. What do they want the county to be," according to an informed source who asked not to be named. "The zoning board was really afraid that this (the amusement park) would have a negative impact on the county," he added.

The Marriott decision was part of a comprehensive zoning report adopted by the four zoning board members yesterday. The zoning plan does not allow such entertainment complexes to be built in the county.

The section prohibiting a theme park in the county was adopted by a 3-to-1 vote. Ruth U. Keeton was the only board member to favor a theme park in the county. She said it would help create jobs and generate tax revenue and denied that it would have a detrimental impact.

Among other actions taken by the board was the passage of a zoning retriction that limits construction of new homes to lots three acres or larger in the western part of the country.

The proposed Marriott park in Howard county would have featured, among other things, actors dressed as cartoon characters, An estimated 2.6 million customers were expected to visit the park annually, and an estimated $26 million in tax revenues was expected annually, according to Marriott attorney West. The corporation also runs theme parks of a similar nature in San Francisco and Chicago in which rides, exhibits and other entertainment forms evoke early periods of American history.

Howard County currently has a population of 110,000. The eastern section is largely residential, centering on the planned new town of Columbia. With industrial development focused around Rt. 1 and 1-95, the western half of the 165,000 acre country remains largely rural.