Aiming at the localization error of the improved down hole Monte Carlo algorithm, a Monte Carlo mobile node localization algorithm for down hole wireless sensor networks based on signal strength is proposed. According to the change of signal intensity to judge the direction of motion of the node, the sampling area was constructed according to the node position and velocity vector of the previous time. Used one beacon to filer sampling. The simulation results show that the positioning accuracy of the improved algorithm is obviously improved, which is suitable for down hole positioning.