In the current power industry, the raw material for production of insulating paper is mainly softwood of which the growth rate is slow. The fiber length of bamboo is close to that of softwood, and because of its shorter growth cycle and environmental friendliness, it can replace the traditional softwood to some extent. In this paper, insulating oil-bamboo paper and insulating oil-softwood paper with different thermal accelerated aging time were obtained through thermal aging platform. The electrical properties of the two kinds of oil-paper composite materials were compared. According to the research results, although the AC breakdown strength of the insulating oil-bamboo paper is slightly lower than that of the insulating oil-softwood paper in the initial stage of aging, the former decreases more slowly and exceeds that of the insulating oil-softwood paper at the late stage of aging. The relative permittivity of the insulating oil-bamboo paper is significantly higher than that of the insulating oil-softwood paper and the dielectric loss factor of the insulating oil-bamboo paper is relatively higher near 50 Hz but much lower in the low frequencies. It is indicated that the insulating oil-bamboo paper has better structural stability and thermal aging resistance than the insulating oil-softwood paper.