This study was conducted to investigate the relationship among character, nursing professionalism, self-efficacy and self-directed learning ability of nursing students as well as to identify the factors influencing self-directed learning ability. Data were collected from May 22 to June 8, 2017 using a self-report questionnaire and questionnaires from 396 nursing students in J Province. The data were analyzed by t-test, ANOVA, $Scheff{\acute{e}}$ test, Dunnett's T3 test, Pearson's correlation coefficient and hierarchical regression analysis. The mean scores of character, nursing professionalism, self-efficacy and self-directed learning ability were $3.93{\pm}0.47$, $3.83{\pm}0.48$, $3.53{\pm}0.59$ and $3.63{\pm}0.51$, respectively. Character, nursing professionalism, and self-efficacy were positively correlated with self-directed learning ability. The factors influencing self-directed learning ability of nursing students were participation in class, satisfaction with major, awareness of self-initiated life, self-control, will and competence, habit, and self-efficacy, nursing professionalism had no significant effect. Based on these findings, programs that develop character, self-efficacy, and nursing professionalism are necessary for nursing students to promote self-directed learning ability.