In clinical operation, transrectal ultrasound prostate biopsy is the most commonly used method for diagnosing prostate cancer. During operation, the doctor has to hold the ultrasound probe for repeated adjustments all the time, which is difficult to ensure the efficiency, accuracy and safety of the operation. In this paper, through analyzing the transrectal ultrasound guided prostate biopsy operation procedure, a 7DOF passive transrectal ultrasound probe position and posture adjustment remote center mechanism is designed. The posture adjustment module designed based on double parallelogram mechanism realized the centering function of the ultrasound probe, and the kinematics analysis of the posture adjustment mechanism was carried out. The working posture and centering effect of the ultrasonic probe at different feeding distances was simulated based on SimMechanics. The physical prototype of the passive transrectal ultrasound probe position and posture adjustment mechanism was developed and measured in experiment. The experiment results show that the maximum errors of the azimuth angle remote center point motion and the pitch angle remote center point motion of the ultrasonic probe are 4 and 34 mm, respectively, which are less than the deformation of 6 mm that the anus can bear. The random error correlation in different directions is weak, the confidence interval width of the remote center point motion error of azimuth and pitch angles are less than 25 mm, and the maximum relative fixed point error and the maximum relative standard error are 1473% and 1498%, respectively. Therefore, the simulation results, experiment results and the measurement error analysis verify the effectiveness and stability of the centering performance of the proposed transrectal ultrasonic probe position and posture adjustment mechanism.