Abstract: The development of formation tester has made great progress in our country in recent years.Pumping-style formation tester has substituted RFT gradually in drill stem test,which has displayed a brilliant application foreground.To fully exert the advantage of pumping-style formation tester,we should understand the potential accidents while testing.This paper briefly analyze the influence factors、diagnose methods and preventive actions to avoid tool stuck,which provides safety basis for pressure testing and fluid sampling process.