A plastic product manufacturing method includes (a) providing a cloud server which stores a machine number and machine parameters of an all-electric injection-molding machine that includes a controller; (b) downloading the machine parameters from the cloud server according to the machine number; (c) executing mold flow analysis software to generate model data and optimal injection conditions of a mold according to the machine parameters; (d) setting a mold number and a password to the model data and the optimal injection conditions and then storing the same in the cloud server after packaging; (e) connecting to the cloud server using the machine number, the mold number, and the password by the controller; (f) downloading the optimal injection conditions to the controller after the cloud server confirms the machine number, the mold number, and the password; and (g) driving the all-electric injection-molding machine by the controller according to the optimal injection conditions.