Due to the variety of financial markets, stock portfolio optimization is an attractive research topic. In the past decades, many evolutionary-based algorithms have been proposed to optimize different types of stock portfolios, and one of them is named diverse group stock portfolio (DGSP). However, this study found that three problems remain to be solving in the existing DGSP approaches. They are how to set an appropriate group size, evolution process is time-consuming, and difference between risks of portfolios is too high. To solve these problems, two approaches by grouping genetic algorithms (GGA) are proposed for optimizing DGSPs in this thesis. The first approach is used to deal with the first two problems. For setting an appropriate group size, the two attributes, Return on Equity (RoE) and Price Earnings Ratio (P/E), are utilized to group stocks. Then, cluster validation factor, which is used as a part of fitness function, is designed to derive better stock groups. To solve time-consuming problem, a temporary chromosome is designed to reduce number of stock portfolios should be evaluated to speed up the evolution process. The second approach is then proposed to handle the third problem. It first designs risk ratio factor to calculate the maximum risk of a given DGSP. Then, by combining adaptive crossover, adaptive mutation, and rank-based roulette wheel selection, the second approach has higher searching ability to find better solution. At last, experimental results on the two real datasets that contain 31 and 50 stocks were made to verify the two proposed approaches are effective and efficient. Comparing with the existing approach, the results show that the first approach can not only reach similar return but also reduce execution time up to 85%. The risk of optimized DGSP by second approach is significantly lower than that by the existing approaches.