This study was conducted to investigate experimentally the effect of track tension on the tractive performance of rice combine. The experiment was carried out at the two in-door soil bins with soil types of loam and sandy loam. The initial track tension was varied by three different values of 0.71, 1.75 and 3.84kN at three different forward velocity settings of 0.17, 0.32 and 0.45m/s, respectively. The data acquisition system was designed and used for the measurement of pull, driving axle torque and its velocity under the test conditions to calculate the tractive efficiency. Results of the study were summarized as follows : 1) The effect of the initial track tension on the tractive efficiency was found being significantly dependent on soil types but not on forward velocities. Therefore, the benifit of adjusting the initial track tension may be obtained when the types of soils on which combines operate are changed. 2) In loam, tractive efficiency decreased with increase in track tension. However, it increased in sandy loam until it reached to a peak value and then decreased with increase in track tension. 3) The maximum tractive efficiency of the tested combine was obtained with an initial track tension of about 1.75kN on sandy loam, and below that on loam at about 5% slippage without being noticeably influenced by the forward velocity.