Direct driven hydraulics (DDH) is receiving increasing attention due to its advantages such as high energy efficiency, easy maintenance, and compactness. However, its oil contamination management has not been surveyed in detail, whereas uncontrolled oil contamination might result in extra maintenance efforts or even downtime. Therefore, this research paper analyzes the oil filtration in direct driven hydraulics through modeling and simulation to predict the filtration effects and support the filtration design. Firstly, model blocks of the filtration characteristics are built to be added to the basic DDH dynamic model. The model can hereby include the coupling effects between fluid degradation and component wear, the filtering process, and the time-varying filter performance. Secondly, the proposed model is applied to a DDH that incorporates filtration and simulated under a duty cycle for 960 hours. The DDH efficiency and control performance when considering the contaminant are revealed. Thirdly, the results are compared between different filter selections and a filtration solution is finally proposed. In conclusion, this paper illustrates the filtration effects on the efficiency, control performance, and oil contaminant level of DDH by simulation, which can hereby support the design of the DDH filtration solution. According to the simulations, the filtered DDH resulted in 96% degradation of the pump's volumetric efficiency after 960-hour running compared to 92% when not using any filters. The extra pressure drop introduced by the filter is below 2 bar, suggesting that the introduction of a filter with 6 μ m filtration level is beneficial.