Abstract: Gem microscope is an essential instrument in routine inspection and the research of jewelry.Gem microscope generally consists of amplification system,bracket system and light source system.The light source system of traditional gem microscope has obvious defects and deficiencies.In view of imperfects,the authors focus on the design and renovation of top illuminant,bottom illuminant to create a new gem microscope in order to improve the image quality by top illumination,bright field illumination and dark field illumination.In additional,the added and designed polarizing optical system makes it effective observe the extinction phenomenon by crossed polarizing filters and interference figure,which plays an important role in the determination of optical and axis character.This paper focuses on the functions and image quality and extra function of the new gem microscope after improvement.For highlighting the new gem microscope design and practicality,the authors make some comparisons on the functions and image quality.