This study aims to determine the internal factors and macroeconomic factors that affect the underwriting surplus (deficit) of tabarru' funds in Islamic life insurance companies in Indonesia. Internal factors used are contributions, investment returns, and claims. And macroeconomic factors used are inflation and Gross Domestic Product (GDP). The research sample was taken by purposive sampling technique, namely as many as 20 sharia life insurance companies. The observation period begins in 2017 and ends in 2020. The analytical method used is panel data regression analysis which is processed using Eviews 10. Based on the panel data regression test results show that simultaneously contributions, investment returns, claims, inflation and GDP have a significant effect on the underwriting surplus (deficit) of tabarru' funds in sharia life insurance companies in Indonesia for the period 2017-2020. Partially shows that contributions, investment returns, claims and GDP have a significant effect on the underwriting surplus (deficit) of tabarru' funds in Islamic life insurance companies in Indonesia for the period 2017-2020. Meanwhile, inflation has no significant effect on the underwriting surplus (deficit) of tabarru' funds in Islamic life insurance companies in Indonesia for the period 2017-2020.