Anti-lock brake systems are nowadays very popular in automobiles and even in sport motorcycles. They improve the vehicle's stability during the braking process, but on the other hand, they also increase the vehicle's cost. Motorbikes are popularly used as personal transport means in Vietnam and other developing countries. Most of them are not equipped with ABS, and a large percentage of traffic accidents in these countries are related to motorbikes. This paper presents a proposal for a simple anti-skid brake system for motorbikes. Two-state pressure modulator was used to regulate brake pressure in the pressure-increasing state and the pressure-decreasing state. A control algorithm was proposed for the system with the two-state pressure modulator. The proposed system was mathematically simulated on a computer, and an experimental prototype was simulated on a real road. Both mathematical and experimental simulation results are presented in the paper.