Hong Kong's clothing manufacturers will have to make greater use of computers and machines if they want their industry to stay on its success path, Hamish Macleod, Hong Kong's trade and industry secretary, said.

The government is determined to combat the threat of protectionist measures in overseas markets. But the industry itself must continually upgrade skills and infrastructure if it is to remain competitive, Mr. Macleod said in his speech Tuesday at the opening of the annual industry fair.The fair - which features some 80 companies from the United States, Europe, Japan, and Hong Kong - is expected to draw more than the 20,000 visitors who attended the last fair. The expected turnout has lead officials to call this year's fair the largest ever held.

The show is organized by the Hong Kong Productivity Council, a government- aid ed entity whose mandate is to make Hong Kong industries more efficient. The agency's own exhibits include automatic sewing systems, cloth-spreading

machinery, cutting and pressing equipment and a variety of computer-aided gear still fairly novel in Hong Kong.

Protectionism aside, perhaps the biggest challenge to the industry is to meet the demand for quick response, said S.H. Sy, training consultant to the productivity council.

Quick response is now the key issue. The communications gap between manufacturer and seller is narrowing because of computers. Buying houses expect to receive goods much faster than previously, often within two or three months, Mr. Sy said.

The other significant change in the industry is the preference among buyers for a greater number of smaller orders, rather than a small number of big orders.

Orders that used to be taken in thousands of dozens are now being taken in hundreds of pieces, Mr. Sy said.

This development is a direct result of greater use in the industry of computer-aided design and manufacturing (known as CAD/CAM), and other new technology to improve efficiency, he said.

The productivity council offers 500 training courses and seminars each year, as well as in-house sessions tailored for individual factories. It has also developed computer software including management information, payroll and knitwear design packages.

While the textile and apparel industry is the colony's largest export earner - employing one-third of all industrial workers - most of its manufacturers run small operations. Owners are reluctant to spend heavily on research and development or fancy equipment, despite government urging.

Apparel exports earned HK$41 billion (US$5 billion) last year - not counting footwear and knitted goods - up 23 percent from the HK$33 billion of 1986, according to Census and Statistics Department figures.

In the first 10 months of last year, the United States took nearly US$3 billion worth, or just over half of total exports to that point, keeping it firmly in No. 1 position. The 10-month figure represents a jump in U.S. sales of 24 percent over the corresponding 1986 period.

But the U.S. share of Hong Kong's clothing exports is declining rapidly. Sales to Japan for the January-October period were up 77 percent and to the European Community 33 percent.