Methods for optimizing gain of an ultrasound image may include: acquiring a tissue image and a first noise image under a same imaging condition; de-noising the tissue image by the first noise image to obtain a de-noised tissue image; identifying a tissue region in the de-noised tissue image; determining whether a percentage of the tissue region in the de-noised tissue image exceeds a preset threshold condition; selecting, according to the determination result, a corresponding calculation method to calculate a first master gain and a first time gain compensation (TGC) curve for the tissue image; and applying the first TGC curve and the first master gain obtained through calculation to the tissue image acquired before.