Following an astonishing year of earnings, MCI Communications Corp. yesterday announced a 2-for-1 split.

To the hearty applause of shareholders during the company's annual meeting, MCI Chairman William G. McGowan announced that the company had approved the stock split early yesterday morning.

The split represents a major event for the local company, which only six years ago was on the verge of bankruptcy as it struggled to become a competitor of American Telephone & Telegraph Co.'s long-distance service.

At that time, the price of MCI stock was at its low of $1.50 a share. Yesterday, with MCI firmly entrenched as AT&T's major long-distance competitor, the price of the company's stock closed at 42 3/8, down 1/2, just $16.75 below that of its chief competitor, AT&T. In the over-the-counter market, 1,658,700 shares of MCI traded yesterday.

The split is effective Sept. 10 for all shareholders of record at the close of business Aug. 3.

The current stock price--more than double that of a year ago--in large part reflects the company's earnings record over the past year. For the fiscal year ended March 31, MCI earned $86.5 million, more than four times the previous fiscal year's profits of $21 million.

Revenues for the last fiscal year more than doubled that of the previous year, going from $234 million to $506 million, and financial analysts predict that revenues will be more than $1 billion for the current fiscal year--a prediction McGowan has not disputed.

For its first quarter ended June 30, MCI earned $36.5 million (75 cents a share) on revenues of $185 million. These figures reflected increases of 115 percent in revenue, from $86 million, and 242 percent in profits, from $10.7 million, over the same quarter a year ago.

The many business ventures that MCI is entering will generate part of the increase in revenue. The company's just-completed acquisition of Western Union International, one of the nation's leading international data transmission companies, places MCI in a key position to expand into the international telecommunications market, McGowan said.

"The meek shall inherit the world, but they'll never increase market share," McGowan told stockholders.