[en] The main purpose of motor-operated valve(MOV) dynamic test is to get the differential pressure(DP) thrust necessary for moving the valve disc to safety position under conditions with design basis flow and differential pressure. DP thrust is defined as the product of valve factor(VF), the mean seat area and DP. Valve factor can be directly calculated by using measured stem thrust and DP. Some MOVs may not be tested or be tested under DP less than design basis DP due to the safety concerns, system characteristics, or improper testability. The operability of these valves can be usually verified with VF values obtained from other dynamic tests. Therefore, It is important to properly determine the valve factor for conservative estimating the operating margin of valves untested or tested under less DP condition. In this paper, behaviors and distribution of measured VFs, which are calculated from the results of dynamic tests performed by september of this year in domestic PWRs, have been evaluated. As a result, conservative valve factor is observed at the point of maximum thrust in case of atypical behavior of stem thrust (hooking and humping). In case of typical behavior, the highest VF has to be chosen between running point and just-before-initial wedging in closing stroke, and between just-after-unwedging and running stroke in opening stroke. It is also found that measured valve factors are distributed with wide error bound even in the valves with same vendor, same size, and same operating condition