This study examines and analyzes how the impact of Covid-19 on the formation of an optimal portfolio using the Single Index Model and measuring optimal portfolio performance using the Sharpe index, Treynor index and Jensen index. The sample data of this study uses stocks listed on the Indonesia Stock Exchange, especially those listed on the LQ45, MNC36, IDX30 and Bisnis27 indexes for the period 1 March 2020 - 31 May 2022. This study aims to analyze portfolio composition, analyze portfolio returns and risks, and analyze portfolio performance formed during the Covid-19 pandemic. The results obtained that the optimal portfolio formed in the LQ45 index is 20 stocks, the MNC36 index is 12 stocks, the IDX30 index is 11 stocks and the Bisnis27 index is 14 stocks. The optimal portfolios that are formed all produce an expected portfolio return that is greater than the level of risk, and is higher than the markets expected return and also higher than the risk-free return. The results of the analysis of the most optimal portfolio performance during the Covid-19 pandemic, namely a portfolio formed from LQ45 index shares, this index deserves to be an investment choice for investors. Evaluation of the optimal portfolio formed results in realized returns greater than expected returns and also greater than risk-free returns. This study shows that the formation of an optimal portfolio during the Covid-19 pandemic using the Single Index Model provides positive returns.