This paper deals with the estimation method on the initial pole position of a z-axis permanent magnet linear synchronous motor(PMLSM) without magnetic pole sensors such as Hall sensors. The proposed method takes account of the gravitational force at z-axis and also the load conditions. The algorithm consists of two steps. The first step is to approximately estimate the initial q-axis by monitoring the movements due to the test current at predefined different test q-axes. The second step is to estimate the real q-axis as accurately as possible by using the outputs corresponding to torques due to the test current at three different test q-axes in order to avoid the effect of load mass variations. Experimental results on the z-axis PMLSM show good estimation characteristics of the proposed method irrespective of load mass conditions.