The present invention discloses a phosphorus-free, green and environment-friendly slow-release scale inhibitor, which comprises the following raw materials in weight part: 5-20 parts of maleamic acid, 5-10 parts of chitosan, 2-5 parts of lignin, 1-10 parts of starch, 3-15 parts of sodium humate, 1-3 parts of polyacrylic acid, 2-10 parts of sodium molybdate, 1-5 parts of zine stearate, 4-10 parts of zinc borate, 3-12 parts of sodium lactate, 1-8 parts of triethanolamine, 3-10 parts of benzotriazol, 5-20 parts of polyaspartic acid, 3-12 parts of S-CETSA, 10-25 parts of polyepoxysuccinic acid, 2-15 parts of acrylic acid-2-acrylamide-2-methyl propane sulfonic acid copolymer and 50-70 parts of water. The phosphorus-free, green and environment-friendly slow-release scale inhibitor is phosphorus-free, non-toxic, green, environmentally-friendly, and good in scale-inhibition and slow-release effect.