Abstract: To investigate the biodegradable properties of chrome-free leathers, Penicillium sp. was used to degrade vegetable-tanned and aldehyde-tanned hide powder. The changes in the structure and thermal properties of tanned hide powder before and after degradation were analyzed by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analyzer (TG), differential scanning calorimetry (DSC) and micro hot table (MHT). The degradation degree of tanned hide powder by Penicillium sp. was characterized by monitoring the pH, hydroxyproline content, and total nitrogen content in the filtrate during the degradation process. The results show that Penicillium sp. exhibits certain degradation effects on both types of tanned hide powder. The surface morphology and structure of hide powder fibers are damaged to varying degrees, and their thermal stability and resistance to thermal decomposition are reduced. While Penicillium sp. has a greater impact on the thermal stability of vegetable-tanned hide powder, it causes a more severe disruption to the thermal decomposition stability of aldehyde-tanned hide powder. Due to changes in the pH and nutrition content of the filtrate during the degradation process, the degradation efficiency gradually declines. As vegetable-tanned leather powder is more susceptible to pH-induced detanning, it shows better degradation performance than aldehyde-tanned hide powder. In summary, the degradation of chrome-free tanned leather by Penicillium sp. results from the combined effect of detanning and microbial metabolism of tanned collagen.