The invention relates to an environment-friendly chemically nickel plating brightener. The brightener consists of 0.5 to 1.0 g/l of 1, 5-naphthalenedisulfonic acid, 0.1 to 0.15 g/l thiourea, 0.8 to 1.5g/l ferrous ammonium sulphate, 1.0 to 1.5g/l of coper sulfate, 30 to 45g/l citric acid, and the residual quantity of water. The ingredient of the brightener is free from heavy metal ions such as lead ion and chromium ion, which is harmless and environment friendly. When the brightener is applied to the chemical nickel plating solution and the to-be-plated work pieces are plated, the brightness of the plating layer can reach or be superior to the brightness effect of a brightener containing CdSO4, and the plating layer is compact, nonporous and hard. Furthermore, the brightener can function as a stabilizer, therefore, when the brightener can be applied to the chemical nickel plating solution without adding a stabilizer.