The ultra-large microwave-transmitting antenna has attracted great research interest in Space Solar Power Station (SSPS). This study aims to explore the design of a new type of ultra-large planar deployable structures for SSPS. This structure has the merits of a large folding ratio and reliable new driving/locking systems with high stiffness. The primary novelty is the new planar deployable structure, of which the basic module is composed of three square units. On the opposite sides of the square unit, torsion springs in the driving/locking systems provide the driving force for deployment. There are three types of driving/locking systems and two types of member bars in each planar deployable structure, which can deploy in both horizontal and vertical directions from the initial folded state. In the thickness direction, there exists an option between deployable (with driving/locking systems) and undeployable (without driving/locking systems) scheme. We describe the design details and working principle of driving/locking systems. The deployment of the basic module is then simulated. Considering the carrying capacity of the future heavy launchers, a large deployable subarray, which consists of the repeating modules, with a full length of 50 m and a width of 7 m is designed and analyzed. Moreover, the initial folded size of the subarray is only 4.8 m × 4.8 m. Finally, we propose a SSPS model with one 200 m-caliber antenna composed of multiple subarrays and two 600 m-length solar cell arrays. Dynamic analysis for this SSPS model shows that the stiffness of this basic deployable structure satisfies the requirements of ultra-large SSPS's performance.