This study was carried out to investigate the compressive strength and the other effects varying to seasons and curing days on the wet curing conditions of the plain concrete. The results obtained are summarized as follows; 1. The longer the wet curing days and the higher the temperature, the greater the compressive strength was expected. 2.。$_2$8, compressive strength of concrete at 28 days under the dry curing conditions showed a range in 64-76% of that under the wet curing conditions. 3. The seasonal variations in the compressive strength under the wet curing showed in order of summer>spring=autumn>winter, and that under the dry curing were in order of spring ≒autumn> summer> winter. 4. In order to obtain 90% of the design compressive strength, 7 days in spring or autumn and 2 weeks of the wet curing in summer were required. 5. The compressive strength of concrete under the wet curing by using wet straw bag cover was almost the same as that of water curing method. 6. Under the wet curing conditions, the higher the temperature, the greater the effect of the curing of concrete was obtained, however, the compressive strength of concrete was decreased under relatively higher (over 15$^{circ}$ C) and lower temperature (below 4$^{circ}$C). 7. Freezing damage was occured when temperature was below 0$^{circ}$ C and humidity was relatively high. 8. A considerable differnce between estimation of $^{circ}$$_2$8 from $^{circ}$7 and measured one was appeared in case of the dry curing conditions. Oregon formula was appeared to be acceptable under the wet curing conditions. 9. In relationship between $^{circ}$$_2$8 and $^{circ}$7~, $^{circ}$28=1. 52 $^{circ}$7 under the wet curing conditions except winter season, and $^{circ}$$_2$8 =(1.39-1, 48)$^{circ}$7 under the dry curing conditions were shown.