Objective To explore the effects of mother's dietary quality in the second and third trimesters on infancy neuropsychological development in order to provide evidence for reasonable dietary guidance among pregnant women. Methods Based on Xuanwei prospective prenatal cohort study in Yunnan, infant follow-up was conducted from alive birth to 1-year age. The dietary quality of pregnant women was evaluated by dietary balance index-pregnancy (DBI-P) based on dietary intakes obtained by 3-day 24-hour food recall and food frequency questionnaires in the 2nd and 3rd trimester of pregnancy from the Xuanwei study. Infants' neurodevelopment was assessed by Bayley Scales of infant and Toddler Development‑Third Edition (BSID-III). A multivariate logistic regression analysis was conducted on the associations between DBI-P in the 2nd and 3rd trimester pregnancy and neurodevelopment of children aged 1 year. Results A total of 409 mother-infant pairs were involved in the analysis. The means of high bound scores (HBS) in the second and third trimesters were 4.77 ± 0.27 and 4.11 ± 0.24 respectively, mainly in suitable and almost suitable status. The means of low bound scores (LBS) were 25.60 ± 0.49 and 26.55 ± 0.51, respectively, showing a low and moderate dietary imbalances. The diet quality distance (DQD) scores were 30.37 ± 0.41 and 30.67 ±0.43 respectively, mainly in low dietary imbalances. The proportions of children with developmental delay in cognitive, language, motor, social emotional, and adaptive behavior development were 8.31%, 21.62%, 17.08%, 5.62%, and 31.49%, respectively. Multivariate logistic regression analysis found that low and moderate imbalance of HBS in the 2nd trimester increased the risk of infancy motor developmental delay (OR=2.52, 95%CI: 1.10, 5.76;OR=7.31, 95%CI: 2.38, 22.44). Meanwhile,low imbalance of HBS in the 2nd trimester increased the risk of infancy adaptive behavior developmental delay (OR=1.95, 95%CI: 1.01, 3.74). Conclusion The dietary quality of rural women in Yunnan during the mid and late pregnancy was mainly low or moderate imbalance. Low and moderate imbalanced dietary with excessive intake of cereal, meat and poultry in the mid pregnancy delayed infancy development in motor and adaptive behavior.