Objective To investigate the effect of positive writing on benefit finding and positive affect of primary caregivers of patients with advanced lung cancer.Methods Eighty-eight primary caregivers of patients with advanced lung cancer hospitalized in two similar wards were allocated into two groups using coin toss method, with 44 in each group.The control group were given conventional health education, while the intervention group received positive writing intervention for five weeks.The Chinese version of the Benefit Finding Scale and the Positive Aspects of Caregiving were used to evaluate the effect before and after the intervention.Results The scores of benefit finding and positive affect in the intervention group were significantly higher than those in the control group (both P＜0.05).Conclusion Positive writing can enhance benefit finding and positive experience of caring in caregivers of patients with advanced lung cancer.