It's studied in this paper that the fire protection problem in the "three dimension (3-D)" of future city traffic. The authors point out that it is different from the pattern of traditional city traffic, analyze the main factors influencing a city's traffic, put forward the suggestion that the fire protection problem of traffic should be solved firstly to realize the idea of part of a city's functional constructions underground. The future problem is mainly as follows: traffic congestion, many hidden dangers, high intensive degree, high risk of fire hazard and so on. With the help of high technology, the problems of traffic's fire protection pre-warning, quick response and emergency evacuation will be solved conceivably. Therefore, the authors draw the conclusion that it is important to prevent and control fires effectively, extinguish fire in time, and evacuate population safely to realize the "three dimensional (3-D)" future city by "3-D" net-system about surveillance and elimination of risks.