This study investigated the intellectual development characteristics and core symptom of Autism spectrum disorders (ASD) children, and explored their relationship between the clinical manifestations with intellectual development level. 280 children (average age=5.09(4-5.67) years) with ASD were enrolled. The Gesell Developmental Scale (GDS) and Childhood Autism Rating Scale (CARS) were respectively used to assess children’s intellectual development and core symptom. We found more female than male with profound intellectual developmental delay in ASD children (P<0.05); and we found that ASD children at 24 to 36 months of age were more likely to be in borderline intellectual ability than being at other months of age (P<0.05). The GDS severity was milder in younger ASD children compared to older ones (P<0.05). There was a positive correlation between ASD symptom severity and GDS total severity (Kendall’s tau-b=2.227, P=0.000). These cores of all GDS functional areas of severe ASD children was significantly lower than that of mild-moderate ASD children, function areas Development Age (DA) of children with mild to moderate ASD was mainly 12 to 24 months, while the language development level of children with severe ASD was lower, mainly at < = 18 months of age level, in which 40.1% is lower than 12 months. We should not only focus on ASD children core symptoms, but also pay attention to their clinical phenotype severity with intellectual development level, considering the impact between the two factors, especially their language ability in different symptom severity, and formulate an intervention plan that fits theirs.