SOUTH China Brokerage net profit surged 63.96 per cent to $138.35 million for the year to December 31 on the heels of active stock trading. Fully diluted earnings per share were 35.3 cents, up 25.62 per cent on the previous basic earnings per share of 28.1 cents. Basic earnings per share were 39.8 cents for the year. The directors have recommended a final dividend of eight cents per share, and a special bonus of two cents per share. The company was listed only last year. Chairman Robert Ng Hung-sang said: ''The Hong Kong stock market was very active in 1993, especially in the last quarter . . . The group made use of the opportunities in the stock and HSI (Hang Seng Index) contracts markets and achieved a very good return.'' Turnover rose 48.39 per cent to $334.37 million for the year. ''The group benefitted from the high turnover, with commission income increasing by 27 per cent as compared with 1992,'' said Mr Ng. The enlarged capital base from its new issue also allowed the group to expand margin finance business, he said. With substantially increased turnover on the stock exchange in the last quarter - more than $7 billion daily - the company's interest income from its margin finance activities increased by 23 per cent. ''The upsurge in the stock market also led to a sharp increase in turnover in the HSI futures contracts in 1993. Interest from clients on HSI futures contracts trading rose substantially, resulting in an increase in commission income by 24 per cent,'' hesaid. ''As the economies of China and Hong Kong continue to prosper and the interest rate is still at a low level, the market should stabilise after recent high volatility,'' Mr Ng said. As more investors were using index futures contracts and options as a means of arbitrage, the turnover in stock and futures markets should continue to be high, he said.