The utility model discloses a film forming device capable of externally adjusting the pH value of liquid drops. The film forming device comprises a liquid drop spray head, a moving mechanism and a base plate fixed on a moving table of the moving mechanism, a working cavity is formed above the moving table; the film forming device is further provided with a pH adjusting device, the pH adjusting device comprises an acid and alkali liquor supply device and an atomization device, a pipeline for connecting the acid and alkali liquor supply device and the atomization device is arranged between the acid and alkali liquor supply device and the atomization device, and an atomization nozzle of the atomization device is located in the working cavity. According to the utility model, pH adjustment canbe carried out on sprayed micro-droplets from the outside, so that the pH value is controlled in the film forming process, and the requirements of uniform film deposition and pattern forming are met.