Global stock exchange markets, counter acceptance between firms in different markets, besides, increasing trading tools, brokers and also online trading, make increase work hours at big markets of the whole world. Today, it caused, stock exchanges by help of advanced technology, go to increasing meetings, trading time, and probably 24-hours trading. Supplying varied financial markets in the country and trading in other countries' stock exchange markets (online trading), make new choices for the investors, Inattention to international and environmental changes ruins Tehran Exchange of competition. Exchanges and brokers by diversification trading performance methods try to informed their costumers’ demands in a best way. The competition of demands procedure among different trading systems is so intensive that make exchanges and online networks advance their demands performance systems according to uniformity with current rules changes. Tehran Exchange follows increasing trading and market’s value by using opportunities of introducing online trading systems (DMA) and more time for trading through welcoming to universal trends and adopting long term guidelines. Otherwise, There would be the risk of lacking most of the market investors who will choose another investment opportunities. In this research we studied six effective indexes of investors usage of online trading systems, including: developing infrastructural hardware (Hardware), security of online systems (Security), technology of software systems (Technology), internet trading rules (Rules), acculturation of online purchasing stock (Culture), and training investors (Education), and their effectiveness on increasing transaction size by using experts' theories and gathering investors and experts opinions by distribution of questionnaires in Tehran Stock Exchange Organization, and by helping fuzzy inference system, it explained condition and importance of each index on volume of transaction.