The invention relates to a machine room air-conditioner outdoor unit dust prevention system which comprises a gate-type framework. The gate-type framework is perpendicularly buckled on a machine room air-conditioner outdoor unit. The two sides of the bottom end of the gate-type framework are each provided with an inverted T-shaped base in a welded mode. One side of the gate-type framework is connected with a net supplying shaft bracket through a connecting shaft, and the other side of the gate-type framework is connected with a net winding shaft bracket through a connecting shaft. A leading net conveying wheel is in shaft connection with a side support. A supporting arm is connected to the side support, and the other end of the supporting arm is in shaft connection with a compressing wheel. The compressing wheel is compressed and abuts against the net winding shaft bracket and the leading net conveying wheel through a spring. One end of a dustproof net is wound around the net winding shaft bracket, and the other end of the dustproof net penetrates through the portion between the leading net conveying wheel and the compressing wheel and then passes through a guiding roller shaft and a supporting roller shaft to be connected with the net supplying shaft bracket. The leading net conveying wheel is connected with a control device. According to the machine room air-conditioner outdoor unit dust prevention system, dust and floating objects can be effectively prevented from entering a machine room outdoor unit, and safe running of the machine room outdoor unit is ensured, the dust prevention purpose of the machine room air-conditioner outdoor unit is achieved, and the air-conditioner using efficiency is improved.