An air spring for rail transit, comprising: an upper plate fixedly connectable to a car body; and an air bag hermetically fixedly connected to the upper plate; and further comprising: an hourglass shaped spring assembly hermetically connected to the air bag, wherein the hourglass shaped spring assembly comprises an hourglass shaped spring and a position-limiting component arranged inside the hourglass shaped spring, the shape of the hourglass shaped spring is a smooth camber, which has a small upper end, and extends downwards gradually to a largest portion, and then is further gradually diminished towards a bottom end, and the position-limiting component comprises a hard boss extending downwards; and the hard boss has a height less than a height of the hourglass shaped spring, a height difference between the hard boss and the hourglass shaped spring is a stop gap of the hourglass shaped spring assembly, a gap between the upper plate and the hourglass shaped spring assembly is a space gap, and the sum of the space gap and the stop gap of the hourglass shaped spring assembly can be configured to be equal to a maximum sinking amount that the car body is allowed. an upper plate fixedly connectable to a car body; and an air bag hermetically fixedly connected to the upper plate; and further comprising: an hourglass shaped spring assembly hermetically connected to the air bag, wherein the hourglass shaped spring assembly comprises an hourglass shaped spring and a position-limiting component arranged inside the hourglass shaped spring, the shape of the hourglass shaped spring is a smooth camber, which has a small upper end, and extends downwards gradually to a largest portion, and then is further gradually diminished towards a bottom end, and the position-limiting component comprises a hard boss extending downwards; and the hard boss has a height less than a height of the hourglass shaped spring, a height difference between the hard boss and the hourglass shaped spring is a stop gap of the hourglass shaped spring assembly, a gap between the upper plate and the hourglass shaped spring assembly is a space gap, and the sum of the space gap and the stop gap of the hourglass shaped spring assembly can be configured to be equal to a maximum sinking amount that the car body is allowed. an hourglass shaped spring assembly hermetically connected to the air bag, wherein the hourglass shaped spring assembly comprises an hourglass shaped spring and a position-limiting component arranged inside the hourglass shaped spring, the shape of the hourglass shaped spring is a smooth camber, which has a small upper end, and extends downwards gradually to a largest portion, and then is further gradually diminished towards a bottom end, and the position-limiting component comprises a hard boss extending downwards; and the hard boss has a height less than a height of the hourglass shaped spring, a height difference between the hard boss and the hourglass shaped spring is a stop gap of the hourglass shaped spring assembly, a gap between the upper plate and the hourglass shaped spring assembly is a space gap, and the sum of the space gap and the stop gap of the hourglass shaped spring assembly can be configured to be equal to a maximum sinking amount that the car body is allowed.