•Two new test benches were built to test the ash’s effect on both deposition and regeneration processes.•Ash is able to lower the pressure drop. 1g/L reaches the lowest pressure drop.•Small diameter ash has negative effect on deposition process, but positive effect on regeneration process.•Mixed ash has positive effect on both deposition and regeneration processes. Particulate matter (PM) emissions from diesel engines are a major problem for the environment and human health. Diesel Particulate Filters (DPF) are widely used to remove PM to achieve strict regulatory emission standards for diesel engines. As the amount of PM deposition inside of the DPF increases, the back pressure of the engine rises, which reduces the engine output performance. A periodical heating to regenerate the DPF can effectively solve the above problem but a study of the effect of residual ash is needed. This paper discusses the influence of ash loading, ash particle size, and ash composition on filter performance due to deposition and regeneration processes on two different testing benches. The lowest pressure drop was obtained when the ash loading was 1g/L in the soot deposition process. Larger ash loading was beneficial for reaching higher temperature and regeneration efficiency. The regeneration efficiency increased 47% when ash loading increased from 0g/L to 10g/L, but the regeneration efficiency only increased 4% when the ash loading increased from 10g/L to 40g/L. Smaller diameter ash particles resulted in lower pressure drop, and higher regeneration efficiency. Compared with pure Al2O3 ash, ash mixtures of Al2O3+SiO2 had lower pressure drop and higher regeneration efficiency.