Objective To provide a device and an effective method for tail vein injection in mice. Methods Doing the tail vein injection in mice with the self-designed device which is consisted of constant temperature part, lighting part and holding part. The difficulty and time of injection with and without the device were compared. Results It was faster and more accurate to perform the tail vein injection in mice with this self-designed device. Conclusion Using this self-designed device can significantly improve the efficiency and save the injection time.