The rain-proof box-type mobile generator set avoids direct contact with the sun, rain, wind, sand, and debris, which is conducive to protecting the normal operation of the power generation equipment. It has inlet and exhaust air and maintenance doors. The mobile trailer generator set is suitable for workplaces in outdoor conditions. It can be flexibly and conveniently moved, and is widely used in construction sites, highways, railway construction, and temporary electricity sites. The size of the trailer chassis and rain box is determined by the size of the generator set. Operators can walk around the mobile trailer for easy operation and maintenance. It has high mobility, low center of gravity, compact structure, and safety and reliability.