Abstract: The embodiments of the present disclosure disclose a method, apparatus and system for determining sweet spot region for shale oil in-situ conversion development. The method comprises: determining an output oil and gas potential index according to a Total Organic Carbon (TOC), a Hydrogen Index (HI) and a shale density; determining a heated shale section according to the output oil and gas potential index and corresponding lower limit value of the oil and gas potential index that is determined according to a well arrangement mode and a shale vitrinite reflectance; determining an output quantity according to a thickness and an area of the heated shale section and data of the output oil and gas potential index; determining a Return on Investment (ROI) according to the output quantity and an invested cost; and determining a sweet spot region for shale oil in-situ conversion development by using the ROI.