Purpose of this study is to analyze the comparison of the average abnormal stock returns received by investors and the average stock trading volume activity before and after the announcement of the Covid-19 Pandemic in Indonesia on March 2, 2020 for companies included in the LQ-45 on the Indonesia Stock Exchange. This study uses the average difference test analysis method, and the data analyzed is the average abnormal return of stocks and the average stock trading volume activity in the short-term period, namely ten (10) days before and ten (10) days. after, as well as long-term period data, namely thirty (30) days before and thirty (30) days after the Covid-19 outbreak was announced in Indonesia. Based on the results of data analysis, it states that for both the short and long term periods there are significant differences in the average stock abnormal return and average trading volume activity of LQ-45 company on the Indonesia Stock Exchange after the announcement of Covid-19 on March 2, 2020, which hit Indonesia compared to before Covid-19 was announced. Keywords: Covid-19, abnormal return, trading volume, LQ-45, Indonesia Stock Exchange