The invention relates to a low-attenuation bend-insensitive single-mode fiber, which is used in a fiber communication system and comprises a core layer and three claddings. The low-attenuation bend-insensitive single-mode fiber is characterized in that the relative refractive index difference delta1 of the core layer ranges from 0.1% to 0.30%, the radius R1 of the core layer ranges from 3.5 micrometers to 4.5 micrometers, the three claddings are arranged on the outside of the core layer, the first cladding is an inner cladding tightly encircling the core layer, the relative refractive index difference delta2 of the inner cladding ranges from -0.1% to 0.1%, the radius R2 of the inner cladding ranges from 8 micrometers to 10 micrometers, the second cladding is a depressed cladding tightly encircling the inner cladding, the relative refractive index difference delta3 of the depressed cladding ranges from -0.4% to -0.1%, the delta3 is smaller than the delta2, the radius R3 of the depressed cladding ranges from 12 micrometers to 20 micrometers, the third cladding is an outer cladding tightly encircling all sub-claddings of the depressed cladding, and the relative refractive index difference delta4 of the outer cladding ranges from -0.2% to 0.1%. On the basis of comprehensive compatibility to existing G.652 standards, the low-attenuation bend-insensitive single-mode fiber has an attenuation performance far superior to that of a conventional G.652.D fiber, the microscopic bending requirement of G.657.A1 standards can be met, and application of a dense wavelength division multiplexing system is facilitated.