Objective To investigate the relationship between parameters of frontal ostium and morphological parameters of agger nasi cell and the severity of chronic frontal sinusitis（CFS）. Methods Retrospective analysis of 25 normal patients and 113 patients with CFS, according to the soft tissue density rate（STDR, %），the subjects were divided into groups 0, 1, 2, 3 and 4. The CT data of normal patients and CFS group were used for three- dimensional reconstruction of frontal sinus and agger nasi cell, and relevant parameters were measured．The Kruskal-wallis test was used to analyze the relationship between parameters of frontal ostium and morphological parameters of agger nasi cell and the severity of CFS. Results ①The morphological parameters of the agger nasi cell: the volume, surface area, vertical diameter, anteroposterior diameter, and mediolateral dimension of the nasal nasi cell in the CFS group were larger than those in the normal control group (P<0.05); ②The value of the anterior-to-posterior (A-P) length of the frontal isthmus（FI） and FI cross-sectional area in the CFS were significantly smaller than those in the normal control group (P< 0.05), and the groups 3 and 4 were smaller than those in the group 1 (P< 0.05); ③FI cross-sectional area was positively correlated with FI and FR values (rs=0.606，rs =0.213，P<0.05) and weakly negatively correlated with the volume, surface area and vertical diameter of the nasal nasi cell (rs=-0.154, rs=-0.161, rs=-0.250, P<0.05), and the volume of the nasal nasi cell was weakly negatively correlated with FI (rs=-0.276, P<0.05). Conclusion Morphological parameters of the agger nasi cell and FI value and FI cross-sectional area are involved in the occurrence and development of CFS, and are positively correlated with the severity of CFS.