Using the negative oxygen ion data of 53 stations over Zhejiang Province in 2016, a data quality control method for negative oxygen ions is developed. Then negative oxygen ion resources are evaluated from several indexes, including annual mean and maximum values, daily maximum and minimum values, the proportion of concentration in each grade, and fresh degree, the spatial and temporal distribution characteristics and regional differences of negative oxygen ions in the province are analyzed comprehensively. The results show that the content of negative oxygen ions is higher in southern and western mountains of Zhejiang, and that in the northern plain is lower relatively. The concentration of negative oxygen ions has obvious daily and monthly variation characteristics in Zhejiang Province：the concentration is low in the afternoon (13:00 to 16:00) and high in the evening and morning (22:00 to 07:00). The concentration is high from April to September, and low in winter. The monthly change in mountain and forest stations are the most remarkable. The concentration of negative oxygen ions in mountain and forest regions is kept at the fresh level basically. The levels of fresh, general, not fresh is about onethird each over the shallow hill regions. The not clean level is account for half in plain and scenic regions. The average number of fresh air hours in mountain and forest areas is more than 20 per day; very fresh air is also more than 16 hours. In scenic spots, forest areas, water parks of shallow hills and plains, the fresh air is also over 10 hours per day.