By use of four compression vessels of triangle, square, circle and large circle, the characteristics of the maximum compression stress, the compression force, the relaxation modulus, the restoration force and the restorating strength of rice straw sheaf by changing conditions of straw were determined. The results were obtained as follows; （1） The maximum compression stress σ_<max> increased exponentially with increase of compression ratio c. The order of each maximum compression stress of these section shapes at high compression ratio was as follow, triangle＞square＞circle, and large circle＞small circle. （2） At the range of experimental speed （15 ～ 60 cm/min）, the maximum compression stress was almost constant without regard to the compression speed. （3） The maximum compression stress at the next day after harvest was slightly larger than that at harvest day, but that for a period of five days after harvest decreased by about half of that at harvest day. （4） On the characteristics of compression curves, the relation between compression force F_c and time t was expressed in the form F_c＝α exp βt, and the order of inclination of straightlines on the semilogarithmic coordinate was as follow, triangle＞square＞small circle＞large circle. From the above facts, it was considered that the circular section is desirable than that of triangle or square. （5） On the characteristics of relaxation curves, the relation between relaxation stress σ and lapse time t_l after compression was expressed as in the equation σ= at^<-b>_l, and all the slopes b of straightlines on the logarithmic coordinates were found to be equal without regard to the section or the compression ratio if the straws were the same. （6） The b values at the next day were equal to those at harvest day, but those for a period of five days after harvest decreased slightly. From the above facts, it became clear that the b value indicates the rheological characteristics of straw. （7） The relaxation moduli E（t） increased with the increase of the compression ratio c, whereas the slope for circular section especially for smaller circle was found to be gradual. （8） In Fig. 11, three restoration forces （F_2, F_3, F_4） and the increase restoration force （F_3-F_2） were found to increase with the incerase of compression ratio c and with the decrease of restoration ratio if （see Fig. 2 also）. There was almost no difference between the initial value F_3 of relaxation curve after restoration and the value F_4 after one minute, but F_4 value was slightly decreased from F_3 value when the compression ratio is large and restoration ratio is small. （g） Generally speaking the restorating strength V_R seemed to have a tendency to increase with the increase of compression ratio, but in reality the influence of restoration ratio on V_R does not seem to have a constant tendency due to variation of compression ratio. From the above results, it was expected that the minimum compression ratio would be obtained, the unavailable power for compression would be reduced and the reduction of restoration force depending upon the excessive compression would also be defended, if the minimum force to pull straw from a binding sheaf and the slack of sheaf （restoration ratio） on the marketed grain binders become known.