The invention relates to a gradual 
refractive index bending resistant multimode 
optical fiber, which includes a sandwich layer and a cladding, and is characterized in that the 
radius of the sandwich layer is 20 to 50 microns; the 
refractive index of the sandwich layer is distributed in a gradient 
gradation type, the distribution 
power exponent Alpha is 1.89 to 1.97, and the maximum relative refringence 
delta 1% max of the sandwich layer is 0.9% to 2.72%; the inner cladding is arranged adjacent to the sandwich layer, the 
radius of the inner cladding is 22 to 57 microns, and the relative refringence 
delta 2% is minus 0.02% to 0.02%; and a middle cladding and an outer cladding are arranged outwards the inner cladding sequentially, the middle cladding is a pure 
quartz glass layer, the 
radius of the middle cladding is 32 to 60 microns, the relative refringence 
delta 3% is minus 0.01% to 0.01%. The gradual 
refractive index bending resistant multimode 
optical fiber provided by the invention not only reduces the bending dissipation of the 
optical fiber, but also guarantees that optical 
fiber has 
high transmission bandwidth at a 1300 nm window, effectively improves the light collection and concentration capabilities of the optical 
fiber to LEDs, VCSELs or LDs through increasing the core 
diameter and 
numerical aperture, and improves the 
coupling fault-tolerant capability of luminous devices, namely between the 
light source and the light transmitting device, i.e. between optical fibers.