BEIJING, AUG. 18 -- China's capital city is cleaning up its act in preparation for a major forthcoming Communist Party congress, as unlicensed peddlers, prostitutes and illegal money changers are feeling the weight of a new morals crackdown.

City officials and police began a month-long drive against petty crime last week, detaining so far 3,010 peddlers accused of selling goods without licenses.

The traders paid fines and had all their goods confiscated before being released.

Several of the city's western-style hotels have imposed stricter rules in their discos, apparently in an attempt to curb the presence of Chinese prostitutes.

At "clothing alley" in the eastern part of the city, where numerous money changers accost foreigners while they purchase western-style clothing, the changers are acting with unprecedented restraint.

It once seemed that the police tolerated many of the money changers or perhaps had been bought off by them.

Some money changers continue quietly to operate, offering 600 yuan for $100, which is nearly double the official rate of exchange.

Chinese individuals and enterprises need the dollars to purchase much-desired imported consumer goods.

The crackdown on profiteering was welcomed by many city dwellers, who have complained that they were being exploited by unscrupulous private traders selling food, soft drinks, clothing, and other consumer goods. Some said, however, that they doubted the campaign would have a lasting effect.

But Communist Party leaders apparently want to counter critics who say that their economic reforms have brought back many of the evils of capitalism. They also want to improve the atmosphere before the forthcoming party congress, which is expected to convene in October.

The newspaper China Legal News quoted an official as saying, "we must . . . create a good environment for reform and for the 13th party congress."

According to the official New China News Agency, the number of private businesses in Beijing increased from 279 in 1978, when many economic reforms were first introduced, to 91,749 today.

These businesses employ some 140,000 workers, mainly engaged in repair businesses or service industries such as restaurants or food and clothing stores, according to the news agency.

The new private sector has been able to provide services that state-owned stores have been unable to supply. But the surge of these private businesses has engendered a fast-buck mentality.