Citicorp, the nation's largest banking group, earned $359 million in the second quarter, little changed from its first-quarter performance but slightly higher than analyst expectations.

As expected, the figures were a sharp improvement from the record $2.6 billion loss posted in the second quarter of 1987, caused by the setting aside of a massive $3 billion to cover the bank against problems in Third World loans.The earnings, equal to $1.03 a share, were up from $358 million, or $1.01 a share, in the first quarter of the year. They were slightly better than forecasted by analysts, who estimated a profit of around 90 cents a share.