Objective To explore the relationship between insulin resistance and idiopathic central precocious puberty (ICPP) in girls and the diagnostic value of insulin resistance. Methods Clinical data of 245 girls aged 4 to 7.5 years with low luteinizing hormone (LH) levels (0.2-0.83 IU/L), normal body weight (body mass index standard deviation score between -2 and +2), and early breast development who visited the Department of Pediatric Endocrinology, Henan Provincial Maternal and Child Health Hospital from January 2022 to March 2025 were retrospectively analyzed. According to the Expert Consensus on the Diagnosis and Treatment of Central Precocious Puberty (2022), patients were assigned to an ICPP group (n=123) or a control group (n=122). Correlations between the homeostasis model assessment of insulin resistance (HOMA-IR) and selected indices were assessed. Multivariable logistic regression was used to evaluate the association between HOMA-IR and ICPP, and the diagnostic performance of various indices for ICPP was evaluated. Results HOMA-IR was higher in the ICPP group than in the control group (P<0.001) and was positively correlated with LH peak (r_s=0.467, P<0.05) and the LH peak/FSH peak ratio (r_s=0.444, P<0.05). The multivariable logistic regression model including age, BMI, and basal LH showed that HOMA-IR was closely associated with ICPP (OR=2.756, 95%CI: 1.940-3.913). Receiver operating characteristic curve analysis showed that the areas under the curve for basal LH, HOMA-IR, and their combination in diagnosing ICPP were 0.735, 0.735, and 0.805, respectively (P<0.05), and the combined model had a greater area under the curve than either basal LH or HOMA-IR alone (both P<0.05). Conclusions HOMA-IR is closely associated with ICPP in girls with low LH and normal body weight, and combining HOMA-IR with basal LH improves early identification and diagnostic efficiency in this population.