The utility model provides a floating caliper disk brake, comprising a brake caliper body, a guide pin, a brake support, a brake disk, a piston, a rectangular loop, a first friction sheet, a second friction sheet, and a fastening bolt, the floating caliper disk brake is characterized by adding an assist spring return mechanism, a heat insulation pad, and an oil inlet joint, the floating caliper disk brake is advantaged by increasing return force of friction block, improving brake effect, reducing influence of friction upon brake system, prolonging service lifetime of brake, and enlarging application scope.