In this paper,a research was carried out on the regularities of carbonization temperature,holding time and mass on weightlessness of low rank coal. The experiment showed experiments in a certern range (450°C~700°C,<60min),weightlessness of coal in an increasing trend,the remained volatile content of semi-coke was measured reduce tending to value,ash content increased,fixed carbon gradually increased in the temperature range with the improvement of the carbonization temperature and holding time,also hydrogen and oxygen content of the char decreased,a significant increased in the carbon content,nitrogen and sulfur content was essentially the same. Reactivity of CO2 and semi-coke obtained in different carbonization conditions were better,the response rates are 100% when the temperature exceeded 1000°C. Best condition of dry distillation: carbonization temperature was 500°C~650°C,mass of low rank coal was less than 30g,holding time was between 30 minutes to 40 minutes.