Abstract: Objective To assess the relationship of disease severity of chronic actinic dermatitis （CAD） to photosensitivity profile, disease course, age, onset age, past history of other disorders such as complicated dermatitis or eczema, of patients. Methods To evaluate the severity of CAD, a questionnaire interview was carried out with 71 outpatients clinically diagnosed as CAD. A CAD severity index （CADSI） was calculated according to the answer of interview. Phototest was carried out from February to March in all patients. Patients were divided into 4 groups based on their sensitivity to UVA and UVB, i.e. insensitive to UVA or UVB, sensitive to UVA only, sensitive to UVB only, sensitive to both UVA and UVB. SPSS 11.5 was used for statistical analysis. Results A significant difference of CADSI was observed among patients with different photosensitivity （F = 10.245, P < 0.01）. The average UVA-minimal erythema dose （MED） and UVB-MED values were 38.5 J/cm2 and 32.9 J/cm2, respectively, in patients with a CADSI of ≤10, significantly higher than those in patients with a CADSI of > 10 （3.9 J/cm2 and 13.4 J/cm2, respectively, both P < 0.01）. CADSI value was negatively correlated with UVA-MED （r = -0.559, P < 0.01） and UVB-MED （r = -0.377, P < 0.01）. Also, there was a significant difference in UVA-MED （χ2 = 26.56, P < 0.01） and UVB-MED （χ2 = 18.22, P < 0.01） among patients receiving different treatment strategies. Conclusions CADSI could be applied to evaluate the severity of CAD in recent one year. UVA-MED and UVB-MED are correlated with the severity of CAD in a degree.