There are two types of treaty visas: E-1 treaty trader and E-2 treaty investor. The requirements are set out in the Immigration Regulations. First for either visa, a treaty must exist between the US and the foreign country of which the alien is a national. Here is the link for the treaty list: https://travel.state.gov/content/travel/en/us-visas/visa-information-resources/fees/treaty.html
For the treaty trader visa, the trade between the US and the foreign country must make up the majority of the foreign trade. Finally, there must be a pattern of systematic trade which shows that there is a steady volume of trade.
For the E-2 visa, the investment made into the US corporation must be substantial. There is no set investment required as every entity and set up are different, but it must be a substantial. Next, the investment funds must be placed a risk which means that you cannot just have them sitting in a bank account and expect the visa to be issued. Finally, the investment cannot be marginal which means that there should be income for US employees and maybe even a profit.