Abstract: Plants growing in high [CO2] levels may change with their physiological, morphological and plant chemical features. Photosynthetic rate may be enhanced while respiration may be inhibited. Stomatal density may become fewer while water-use efficiency (WUE)increases with [CO2] increases. Biomasses and yields of plants growing in high [CO2] may also increase, together with the total non-carbohydrate (TNC) and some key proteins and enzymes increasing. But the C: N ratio could become lower. Contents of some elementary element such as N, S and P may decrease. The development of roots and flowers can be also affected by the elevated [CO2] levels. These conclusions, however, are with some kinds of uncertainty. Plants with different photosynthesis paths (C3 ,C4 and CAM) and different vegetation types (natural and artificial vegetation) have the different response to the elected[CO2]. Long-term and short-term responses of the same plants may differ on the other hand, controlled environmental factors during experiments such as light, temperature, water availability, nutrient content, air pollution, even pot sizes applied for experiment, may have a profound effect on the results. This paper reviews some main methods, leading conclusions and existing problems in the experiments of plant growth responses to high [CO2], based on the existed experimental results in some external countries in the past decade.