Since the birth of the high-speed railway, it is growing with the mobile communication demand of train to wayside. One part of traffic load demand is from the train control and train dispatching, which is an important part of the high-speed railway. And another part of the traffic load is from the passengers, which is one of the important Key Performance Indexes (KFIs) that can satisfy the requirement of passenger service quality. Especially in the era of mobile Internet, the Internet demand becomes an important part of peoples daily life. This paper summarizes the important processes of the development of mobile communications for high-speed railway over the world, especially the present mobile communication technologies to support the passengers information access from train to Internet. Based on the development trend of mobile communication technology, the development trend of its counterpart in high-speed railway is discussed, including its relationship with the development of public mobile communication technology. Some future key technologies, including some detailed suggestions, of mobile communications for high-speed railway are prospected, which may provide some references for the relevant researchers in this field.