Abstract: HPHT, CVD lab-grown diamonds and natural diamonds have the same composition and physical and chemical properties, only the environment and trace elements during growth are different. There is no instrument that can fully distinguish lab-grown diamonds from natural diamounds, and multiple types are needed. Instruments or methods include: strong magnetic, microscopic observation, UV-Vis-NIR, deep ultraviolet light, PL, cross-polarization microscope, phosphorescence, thermal conductivity meter, transmission electron microscope, infrared spectroscopy and other cross-comparisons to find out separately of small differences so that the lab-grown diamonds can be fully identified. This article lists and illustrates the identification characteristics of various instruments or methods. UV-Vis-NIR spectrum N3 colour center at 415 nm absorption peak; CVD diamond PL spectrum has a 737 nm peak of Si-V center; CVD lab-grown diamonds under crossed polarization can show a variety of abnormal birefringence fringes; HPHT lab-grown diamonds under phosphorescence will have strong blue luminescence, and CVD lab-grown diamonds will have medium, weak or no luminescence; in thermal conductivity meter test, some HPHT diamonds show MOISSANITE, and some show DIAMOND; CVD diamonds treated by HPHT show infrared spectrum in the range of 6 855, 7 229 cm^-1 and 7 355 cm^-1, revealing several C-H peaks, and these peaks disappear after HPHT colour treatment. In addition to the use of jewelry, the lab-grown diamond industry must actively develop industrial uses in order to survive for long time.