A method and a device for continuously preparing microspheres, and a collection unit thereof are provided. The collection unit for collecting microspheres in the solution comprises a tank and a first plate. The first plate is removably disposed in the tank. The first plate, when lay across the tank, has its two ends came in contact with the sidewall of the tank so as to divide the tank into a first chamber and a second chamber. The tank has an outlet located in the second chamber. After the solution with microspheres are input to the first chamber of the tank, the microspheres are deposited around the first plate, and the solution is caused to pass through or over the first plate to the second chamber and output from the outlet.