Hello everybody, i would like to ask is possible visit Simatai without make reservation in advance?

I'm afraid not. A reservation ahead of 24h before your visit is needed to visit the wall. Although the official website says that the visiting on site is acceptable, it depends on the number o the reservation people on that day (usually there is little chance on the spot). In case of any problem, you'd better make a reservation in advance.

By public bus, the journey from Dongzhimen takes about 3 hours. (You can take bus no. 980 fast from Dongzhimen to Miyun Bus Station, and then transfer to the special line to reach the wall directly)