The advantages of liquid crystal wavefront corrector (LCWFC),compared to conventional DM (deformable mirror) devices,are low cost,reliability,low power consumption,low price,no moving mechanical components and high resolution[1].Due to its high resolution (tens of thousands of pixels) which needs immense computation to calculate control signal,the latency of control loop computation is one of the bottlenecks that hinder its application in on-sky liquid crystal adaptive optics systems (LC-AOS).Here we present a cost-effective real time controller (RTC) for,though not devoted to,a high order LC-AOS,designed for a 2 meter telescope,which is based on a 20*20 sub-aperture Shack-Hartman wavefront sensor with 6*6 pixels per sub-aperture,209 Zernike modes (without piston) for modal wavefront representation[2],and a LCWFC of 65536 (256*256) pixels.With a controller implemented on a single PC with four Intel Xeon E5-4650 Processors (4*8 cores,2.70 GHz) and two NVIDIA Tesla K10 cards (2*2 Graphic Processing Units,with a clock rate of 745 MHz and 1536 cores on each unit) architecture,we achieve a total control loop computation latency of 180 us with an impressive computation speed of 304.3 GFlops (Giga floating point operations per second) on GPUs (Graphic Processing Units).With next generation GPUs or a GPUs cluster,this controller is very promising to support larger AO systems.