Financial markets play a key role in a country’s economy, but a developing economy could not make any progress without a clear financial system. Various factors affect the level of liquidity in financial markets, and one of them is financial openness. Therefore, this study has examined the impact of openness of financial markets on the level of liquidity over a 38 year period (1980 – 2018). Empirical research results show that in countries under study, financial openness has a positive and significant effect on the liquidity level in financial markets. Gross domestic product per capita (GDP), inflation and market’s value also has a positive and significant effect on the liquidity level in financial markets. In other terms, the higher these variables are the higher market liquidity level and vice versa. Also model-based estimation researches show that in Iran only two criteria of Foreign Assets’ (FOA) ratio to G.D.P and Foreign Direct Investment‘s (FDI) ratio to GDP, has a positive effect on liquidity’s level in financial markets.