The present invention relates to a method for drug delivery via brain extracellular space (ECS). It includes putting head of patient in an imaging apparatus generating dynamic images of the brain via the imaging apparatus delivering drugs into brain ECS of the patient according to the dynamic images and the drugs get to the therapeutic target by simple diffusion along concentration gradient. The present invention also relates to a device for drug delivery via brain ECS. Basing on the self-diffusion delivery (SDD) of drugs in brain ECS, the present invention can deliver drug into the ECS of the brains relatively safe area in low speed, with small amounts of doses and without extra stress. Therefore, the present invention can reduce delivery time and dose of drugs, relieve injection pressure, decrease damages on normal brain tissue, and reduce the cost of treatment observably.