The major objective of this study is to assess the financial performance and identify the affecting factors in this performance of non-oil manufacturing companies from 1999 to 2008. The study sample consisted of all non-oil manufacturing companies' enlisted at Libyan stock market which count (8). The data collected was analyzed by using statistical analysis method such as descriptive statistics, correlation test, Multiple- regression, as well as semi-structured interviews method. The results regarding to the statistical analysis method (net working capital, inventory turnover ratio, selling and general administrative expenses ratio, and company size and company age), have a positive statistical effect on the financial performance(ROA), while the variables of (current ratio, quick ratio and account receivable turnover ratio), have a negative statistical effect on the financial performance (ROA). The results regarding to semi-structured interviews method, reveal that the respondents in the interviews were confirmed that the selected factors have a significant effect on financial performance (ROA). The researcher recommended that the selected companies must consider the listed decision on the Libyan stock market; even when their financial performance is good.