The invention discloses a method for evaluating and optimizing radiotherapy dose based on a cone beam CT (Computer Tomography) image CT value correction technology. The method comprises the following steps of: a, collecting image information; b, making an initial radiotherapy plan; c, acquiring a CT value correction table; d, correcting a CT value of a cone beam CT image; e, drawing a target region and an outline; f, setting a current radiotherapy plan; g, judging whether rigid registration needs to be carried out or not; h, evaluating the current radiotherapy plan; j, carrying out local optimization by taking the current radiotherapy plan as the initial plan if the current radiotherapy plan needs to be optimized; k, off-line evaluating the radiotherapy plan; and l, judging whether the radiotherapy plan needs to be regenerated within a global range or not. According to the method disclosed by the invention, the accuracies of the dose calculation and the dose evaluation are ensured, and the fastness and convenience of the online optimization of the radiotherapy plan are also ensured; and the fastness and convenience of the online optimization are ensured by the local optimization, and the accuracy of the optimization is ensured by the global optimization, thus effective therapy on the target region is ensured, and the damage on normal tissues is avoided as much as possible.