Abstract: There are a large number of fallen trees and slopes in forest areas, which leads to complicated terrain. Most of the existing fire engines are wheeled fire engines and Caterpillar fire engines. However, the existing fire engines are limited in passage performance. A large Caterpillar forest fire engine (LF1352JP) was designed in this article. The fire engine was built on the basis of the first generation of Caterpillar forest fire engines (LY1102XFSG30) and performance optimization and transformation were carried out. The chassis of Caterpillar fire engine (LF1352JP) was modified on the basis of the chassis of the original skidding (J-50)crawler tractor, and the engine power increased from 85 to 99.3 kW. The width and length of the chassis were increased on the basis of the original chassis, and the cowcatcher and hydraulic capstan were added on the basis of the original vehicle to ensure the advantages of the existing vehicle function. It maintained the advantages of the elastic chassis of the original vehicle and the large gap from the ground. CREO three-dimensional simulation software was applied to Caterpillar forest fire engine (LF1352JP). The three-dimensional design simulation of the chassis, upper mount, barrier device and waterway system was carried out. The density of each structure was input into the CREO three-dimensional simulation software to simulate the center of gravity. The lateral and longitudinal stability of the fire engine and the performance of the vertical obstacle crossing and crossing the trench were analyzed theoretically. The results are as follows: When Caterpillar forest fire engine runs laterally, its maximum slope angle allowed on the slope at full load is 40.6°, and at no load it is 45.1°; when it runs longitudinally, the maximum longitudinal upslope angle is 52.0° at full load, and 60.9° at no load, and the maximum angle of downslope is 47.2° at full load and 45.8° at no load. The height of obstacle crossing is 405 mm at full load and 615 mm at no load. The width of crossing the trench is 1 248 mm at full load and 983 mm at no load. Compared with the first generation of Caterpillar forest fire engine (LY1102XFSG30), the vehicle has significant improvement in the performance including running upward and downward longitudinally, running horizontally, and crossing the trenches and vertical obstacles. The tests were performed at Yushu in Harbin, Heilongjiang and Yakeshi test site in Inner Mongolia Autonomous region. It included 4 experiments: longitudinal upslope, longitudinal downslope, crossing trenches, and 200 m velocity measurement. When the upslope experiment was carried out, the Caterpillar forest fire engine (LF1352JP) was made in different gears and different slope angles and then its upslope time was recorded, and the result showed that longitudinal upslope maximum angle was 48° according to the actual measurement when the current vehicle was at full load. In the longitudinal downslope experiment, the Caterpillar forest fire engine (LF1352JP) was made in different gears and different slope angles and then its downslope time was recorded. According to the actual measurement when the current vehicle was at full load, the vehicle would show the slipping trend. The maximum span width of crossing trenches experiment was 1 300 mm, which was not enlarged because of the safety considerations of fire engines. The experiment verified the upslope performance and obstacle surmounting performance of the vehicle, and the theoretical analysis results were verified by the experimental results. The performance of LF1352JP fire engine can meet the requirements of mountain fire fighting in complex terrain in forest area. It is a kind of large forest fire engine with excellent performance.