Abstract: Research on the possible effects of Cloud Condensation Nuclei(CNN) on radiant properties of cloud and climate has been investigated in many papers,but the effects of Ice Nuclei(IN)have not been well analyzed.In fact,ice nuclei are very importantin many weather events for the reason that IN can affect the initial concentrations of ice particles in cold cloud and then change the physical characteristics of cold cloud.Recently,with more and more human activities,numerical concentrations of IN have increased a lot in at mosphere in some places. Observations in Beijing show that the concentrations of IN in Beijing have increased a lotin about 32 years from 1963 to 1995.The IN concentrations which can been activated at -20℃ increase about 15 times.Since,ice nuclei concentrations athigh altitudes and the concentrations and scales of ice crystal in cloud can not be observed sy nchronous easily now,so the relation between concentrations of IN and ice crystal by observation we can not be tested in reality.Thus,numerical simulations are adopted.In this thesis,all simulations used 3-D convective cloud model of CAMS(Chinese Academy of Meteorological Sciences,version 2000).First of all,a single test which used the sounding data of June,10,1996 was completed.In the simulation,it is supposed that the concentration of IN had increased 5 times and 10 times and got the same results that ice particles concentration increased and the size of them decreased.What is more,cloud tops heightened when IN concentrations increased although the change ranges were notentirely the same.Then numerical simulations of 18 precipitation days from June to September in 1996 were conducted.The conclusions were that when ice nuclei concentrations increased, in 80 percents simulated precipitation processes,the amounts of precipitation decreased,the cloud tops heigh-tened and the areas of cloud top height increased.rather more,in 95 percents processes,the scales of ice crystal in the cloud decreased and the quantities increased.That is,physical properties of cold cloud changed when IN concentrations changed.From some analysis including a simulation using SBDART radiative model,some results could be achieved.That is,cloud reflectance increased when cloud top increased,ice particles concentration increased and size of them decreased when cloud reflectance increased.In conclusion,radiant properties of cloud changed when IN concentrations increased.For the reason that cold cloud plays an importantrole in global radiative balance,the climatic effects caused by cold cloud can be modified directly and indirectly.