Abstract: The key for improving the naturalness of the syllthetic speech is to build a perfect prosodic model.Thepreliminary study of the influence of selitence stress on prosodic features in Mandarin was described.In continuousbroadcast speech,the relationship between duration and pitch under differellt sentence stress levels is analyzed.Theresults show that:(1) The pitch is the most important factor which carries the selltence stress,along with the increaseof the selltence stress level,the distribution colltour of pitch moves towards high frequency region.(2) In the case of "Stressed" and "Light" ,two peaks are found in the distribution colltour,which means that the duration of some wordsare affected by selltence stress,however others are not.(3) The relationship between pitch and duration in "Normal","Stressed "and" Light"are un-correlated,positive correlation and negative correlation respectively.The research laysa foundation for building a perfect prosodic model for Mandarin speech synthesis system.The results are also used toclassify selitence stress using a neural network,and 63% correction has been obtained in an open set test.A method oflabeling the sentence stress automatically was explored for Mandarin speech database.