Abstract: This paper makes comment on the article“The extent of tropical zone in China”in Vol.11,No.2 of this journal. The tropics,subtropics and temperate zone are divided by temperature indices.Temperature is only one of the climatic elements.Climatic zones are also divided by the other climatic elements.Their extents and borders are very different to each other.Many climatologists do not agree the temperature zones.It is difficult that all of biogeographers,pedogeographers and physical geographers agree to temperature zones. When subdividing physical geographical zone,it should be comprehensively considered to all factors of physical geography,especially the factor of climate.It is not enough to consider the factors of vegetation and soil. The author considers that thermophilous crop,such as rice can be cultivated in whole year,and tropical woody plants,such as rubber tree do not suffer from freeze in tropical zone.The northern boundary of tropical zone coincides with 15℃ isotherm of the coldest month,and 5℃ isotherm of the mean annual minimum.Because the winter monsoon is very strong and very cold in China,so the Chinese tropics situates in the edge of world tropics,its boundary line should not lie too north,but in north of Leizhou Peninsula.