In order to overcome the influence of amplified spontaneous emission (ASE) on the amplified pulse in the femtosecond laser amplifier, it is an effective way to move the Ti∶sapphire from the waist in the cavity to where the size of the beam is largest. The experiments are carried out on such a new-style folded linear Ti∶sapphire amplifier cavity with the large beam size. The relationship between the beam size and the cavity parameters is calculated and the beam size distribution in the cavity is provided. The systemic experiments are done on the relationship between the output power and the cavity parameters such as the radius of the curved mirror, the reflectivity of the output mirror, the length of the two arms and so on.