The Chicago Sun-Times, tabloid champion of the city's working class neighborhoods, was put up for sale today by its owner, Field Enterprises Inc.

The paper, the nation's eighth-largest daily, with a circulation of about 649,000, is expected to be sold as part of a dissolution of Field Enterprises by the company's two shareholders, brothers Marshall Field V. and Frederick W. Field, which was announced today.

One reason for the decision is that Frederick Field wants to pursue his own business interests, the company said.

In a statement read to the paper's staff at a newsroom meeting late this afternoon, the Field Brothers said they were "committed to finding a buyer for the Sun-Times who will continue its record of journalistic excellence and service to the community."

A company spokesman said no talks had yet been held with prospective buyers. But sources said Publisher James Hoge told the assembled staff that he would like to see the paper sold to a large media company such as Knight-Ridder or Times-Mirror Co., publisher of the Los Angeles Times. Hoge also said he would prefer the paper not be sold to New York Post Publisher Rupert Murdoch. The company said that, if no satisfactory buyer is found, the brothers will keep the newspaper through a partnership.

Hoge said the decision to sell the newspaper "came as a surprise to all of us," but staff members said the announcement was greeted calmly--there have been recurrent rumors in recent years that the Sun-Times was for sale.

The company said a decision will be made soon on which assets will be sold, given to one of the brothers or operated as a partnership.

The Fields have owned Chicago newspapers since 1941. The Sun-Times was formed in 1948 by a merger of the Chicago Times and the Chicago Sun and absorbed its sister paper, the Chicago Daily News, in 1978. Publishing editions throughout the day, the recently redesigned Sun-Times has closely trailed the Chicago Tribune in circulation and is the home base of columnists Mike Royko and Ann Landers.

Earlier this week, Field Enterprises completed the sale of its UHF television station in Chicago, WFLD-TV, to Metromedia Inc., and has announced agreements to sell TV stations in San Francisco and Boston. Field television stations in Detroit and Philadelphia are also for sale. The company says, however, that the sale of the TV stations is unrelated to the decision to sell the Sun-Times or break up Field Enterprises.