Bachground: The purpose of present study was to compare biological, cognitive, happiness and spiritual health factors and marital satisfaction among mothers of low birth weight and optimal weight infants in Semnan during 2017-2019 school year. Method:The research method of present study is causal-comparative type of descriptive analysis (post-event). In addition, the present study is based on a fundamental targeting criterion. In order to sampling, 50 people among statistical population of each group were selected through simple random method. Afrouz Biological and Cognitive characteristics scale, Oxford Happiness Questionnaire, Palutzian & Ellison Spiritual Health Questionnaire and Afrooz Marital Satisfaction Scale were used in order to evaluate the research variables. In the present study, descriptive-analytical method was used for statistical analysis. In the descriptive part, multiple logistic regression analysis or Pearson discriminant and correlation analysis were used in SPSS software. Result & conclusion: The findings of Chapter Four showed that there is no significant difference between mothers of low birth weight infants and mothers of infants with optimal weight in terms of age and education (P> 0.05).