Abstract: The purpose of the test is to gain the power reactivity coefficient of the China Advanced Research Reactor (CARR) which is full loaded, and provide data reference for the safety operation of CARR. The control rob grid efficiency calibration method was used in the test. The measurement results in three tests are negative and not inconsistent with temperature reactivity coefficient. It is satisfied with the requirement of the acceptance criteria. The cause about the deviation of the measurement results in three tests was deeply analyzed. According to the actual operation situation of CARR in the future, the result of the third test was used as the power reactivity coefficient of CARR.