A rotary open-close type sun umbrella comprising a standing post, a plurality of umbrella ribs, and a plurality of umbrella cloths, wherein an unfolding device is arranged at the upper end of the standing post, and the unfolding device is rotatably connected with the standing post, wherein the plurality of umbrella ribs are arranged on the unfolding device, and the plurality of umbrella ribs are connected to the plurality of umbrella cloths, wherein each umbrella cloth is connected with two adjacent umbrella ribs, thereby enabling the plurality of umbrella ribs and the plurality of umbrella cloths to be sequentially connected to form an umbrella surface, wherein the standing post is provided with a driving device, and the driving device is in transmission connection with the unfolding device, which allow the umbrella surface to be unfolded or folded, wherein the upper end of the standing post is provided with a steering mechanism, and the lower end of the unfolding device is connected to the steering mechanism in an interacting mode, thus forming an included angle C between the unfolding device and the standing post, wherein the driving device is connected to the unfolding device through the steering mechanism; wherein the unfolding device comprises a plurality of rotating arms, the plurality of rotating arms are sequentially arranged on a same center shaft, and an included angle C is formed between the center shaft and the standing post, wherein one end of each umbrella rib is fixedly connected to a corresponding rotating arm, wherein the rotating arm at the lowermost end in the unfolding device is rotatably connected to the steering mechanism, and a limiting structure is arranged between the rotating arm and the steering mechanism, wherein the rotating arm at the uppermost end in the unfolding device is in transmission connection with the steering mechanism, so that the driving device can drive the umbrella surface to unfold or fold through the plurality of rotating arms; and wherein the steering mechanism is provided with a mandrel, and the lower end of the mandrel is rotatably connected to the steering mechanism through a bearing, wherein the mandrel is arranged within the plurality of rotating arms along a central axis in a penetrating manner, and the mandrel is provided with a plurality of shaft sleeves that correspond to the rotating arms in a one-to-one manner, wherein the rotating arm at the uppermost end in the unfolding device is fixedly connected to the mandrel through a shaft sleeve, wherein the shaft sleeves corresponding to the rest of rotating arms are respectively provided with a bearing, and the rest of rotating arms are rotatably connected to the mandrel through shaft sleeves. a plurality of umbrella ribs, and a plurality of umbrella cloths, wherein an unfolding device is arranged at the upper end of the standing post, and the unfolding device is rotatably connected with the standing post, wherein the plurality of umbrella ribs are arranged on the unfolding device, and the plurality of umbrella ribs are connected to the plurality of umbrella cloths, wherein each umbrella cloth is connected with two adjacent umbrella ribs, thereby enabling the plurality of umbrella ribs and the plurality of umbrella cloths to be sequentially connected to form an umbrella surface, wherein the standing post is provided with a driving device, and the driving device is in transmission connection with the unfolding device, which allow the umbrella surface to be unfolded or folded, wherein the upper end of the standing post is provided with a steering mechanism, and the lower end of the unfolding device is connected to the steering mechanism in an interacting mode, thus forming an included angle C between the unfolding device and the standing post, wherein the driving device is connected to the unfolding device through the steering mechanism; wherein the unfolding device comprises a plurality of rotating arms, the plurality of rotating arms are sequentially arranged on a same center shaft, and an included angle C is formed between the center shaft and the standing post, wherein one end of each umbrella rib is fixedly connected to a corresponding rotating arm, wherein the rotating arm at the lowermost end in the unfolding device is rotatably connected to the steering mechanism, and a limiting structure is arranged between the rotating arm and the steering mechanism, wherein the rotating arm at the uppermost end in the unfolding device is in transmission connection with the steering mechanism, so that the driving device can drive the umbrella surface to unfold or fold through the plurality of rotating arms; and wherein the steering mechanism is provided with a mandrel, and the lower end of the mandrel is rotatably connected to the steering mechanism through a bearing, wherein the mandrel is arranged within the plurality of rotating arms along a central axis in a penetrating manner, and the mandrel is provided with a plurality of shaft sleeves that correspond to the rotating arms in a one-to-one manner, wherein the rotating arm at the uppermost end in the unfolding device is fixedly connected to the mandrel through a shaft sleeve, wherein the shaft sleeves corresponding to the rest of rotating arms are respectively provided with a bearing, and the rest of rotating arms are rotatably connected to the mandrel through shaft sleeves.