Top executive changes were announced today for J. P. Morgan and Co., the prestigious bank holding company which is parent to Morgan Guaranty Trust Co. of New York, the country's fifth largest bank.

Walter H. Page will be the next chairman and chief executive officer of both J. P. Morgan and Morgan Guaranty, succeeding Ellmore C. Patterson. 64, in the position on Jan. 1.

Page 62, currently is president of the bank holding company and its chief subsidiary, and his succession to the top spot had been anticipated.

It was also announced today that Lewis I. Preston, 51, now a vice chairman, will succeed Page in the post of president at the beginning of next year.

Patterson will continue as an officer until his required retirement on Dec. 1, 1978, serving as chairman of the blue-chip banking firm's executive committee.

"This change in my duties at the start of next year is a further part of out transition to a new generation of senior management," said Patterson, who has been chairman for six years and first joined the Morgan bank in 1935 when it was a privately held firm.

Page like Patterson, has spent his entire professional career at the banking house which was founded by financier J. P. Morgan in the 19th century. Page joined the bank in 1937 upon graduation from Harvard College. He returned to the bank after serving the the U.S. Navy in World War II and held a succession of executive posts, joining the board in 1966. When J.P. Morgan and Co. Inc. was formed in 1969 he was elected vice chairman of the holding company. He became president in 1971.