Purpose: The purpose of this study was to identify the effect of relaxation therapy on state anxiety, preterm labor stress, blood pressure, skin temperature, pulse rate of pregnant women with preterm labor and heart rate of their babies. Methods: The participants were 55 pregnant women with preterm labor who hospitalized from May, 2009 to January, 2010. 29 participants were assigned to experimental group and the other 26 participants to control group. All of them were not have any other complications except preterm labor. The relaxation therapy was applied to the experimental group for 5 days. Data were analyzed by the SPSS/WIN 14.0 program. Results: The state anxiety score and the preterm labor stress score of experimental group were statistically significant lower than those of control group. In addition, the systolic and diastolic blood pressure, pulse rate of experimental group were statistically lower than those of control group. The skin temperature of experimental group was higher than that of control group. However, the fetal heart rate of experimental group was not statistically significant lower than fetal heart rate of control group. Conclusion: From these findings, it is concluded that relaxation therapy may be an effective nursing intervention for pregnant women with preterm labor.