Ultrasound Color Flow Imaging(CFI) is widely used in clinical diagnosis.This paper made two improvements for previous research about Graphics Processing Unit(GPU) framework for CFI: on wall filtering block,the parallel regression filtering was implemented instead of Finite Impulse Response(FIR) filter;on post-processing block,the parallel threshold box filtering was added to improve flow uniformity.The experimental data were acquired from a healthy carotid artery: 88 scan lines,510 samples along the scan line,and an ensemble size of 16.The experimental results show that,compared with the serial algorithm based on Central Processing Unit(CPU),the computational efficiency of the proposed parallel algorithms based on GPU has been increased by 15.2 times and the frame rate increases up to 70.The color flow image can achieve a high quality by the regression filter instead of FIR filter,and improve the accuracy of tissue/flow detection by threshold box filter.