A ultra-thin LED bar lights (100) includes a bar house or housing (10), a light module (20), a reflection film (30), a light guide plate (40), and a cover (50) having a light transmittance less than 90%. An angle between the circuit board (22) and the accessory placed board (12) being larger than 80 degrees and less than 90 degrees. The light guide plate (40) includes an incidence wall for receiving the emitted light of the light module, three reflective walls for reflecting light, and a diffusion surface contacting with the reflection film. A width of the diffusion surface of the light guide plate is between 3 times or 4 times the length or the maximum diameter of the LED chips (21) and provides a plurality of light guide points thereon. The light guide points include a plurality of spaced apart circular dots, the total area of which is 50% to 55% of the total area of the diffusion surface.