In this paper, we propose to implement hybrid operat- ing systems based on two-level hardware interrupts. To separate real-time and non-real-time hardware interrupts by hardware, we show that it is easier to build up hybrid systems with better performance. We analyze and discuss the key issues for implementing a hybrid system based on this and implement a hybrid system called RTLinux-THIN (Real-Time LINUX with Two-level Hardware INterrupts) on the ARM architecture by combining ARM Linux kernel 2.6.9 and C/OS-II. We conduct experiments on a set of real application programs including mplayer [20], Bonnie [4] and iperf [13] and compare the interrupt latency dis- tributions for RTLinux-THIN (with and without cache lock- ing), RTAI and Linux on a hardware platform based on In- tel PXA270 processor [12]. The experimental results show that RTLinux-THIN improves real-time interrupt latencies and provides better predictability.