Abstract: This paper describes the occurance frequency of tones and their combinations in Chinese texts.The results show that,there is a difference between dynamic (in usage) and static (in lexicon) occurance frequency of tones and their combinations.It is indicated that speech act is ruled by the less-effort principle,like other human behaviour.The rank order of the occurance frequency of tones in both dynamic and static forms is identical,that is 1.tone-4、2.tone-2、3.tone-1、4.tone-3,namely,tone-4 is used most,then tone-2,tone-1 and tone-3 least.The occurance frequency of tone combinations is related to the number,the position and the structure of syllable combination in polysyllabic words and depends on the rhythm which is one of important factors to construct a polysyllabic word.Tone combinations reflect the principle of less-effort for the speaker and ease understanding for the listener.This principle governs the occurance frequency of tone combinations.Tone distributions in disyllabic,trisyllable and quadrisyllabic words produce their rhythm,it seems that the vibration frequency of vocal cords goes slow gradually in general situation.The results gived above could provide a basis of fUrther study on tone sandhi in Mandarin.The dynamic occurance frequency of tones and their combinations of 2-4 syllable words of Mandarin are also given in this paper.