The invention discloses a method for depositing aluminum oxide through low-frequency PECVD. According to the method, trimethyl aluminum is adopted as a raw material; one oxygen-containing material inO2, water steam and ethyl alcohol steam is adopted as an oxidant; and aluminum oxide is prepared with the low-frequency PECVD method. The method for depositing aluminum oxide through low-frequency PECVD has the advantages of being simple in technique, convenient to operate, low in cost and the like; subsequent plasma processing steps in a conventional method can be omitted; preparation cost is lowered; the technological time is shortened; the yield is improved; besides the aluminum oxide with a better passivation effect can be prepared; and the method is of great significance to preparation ofsolar panels with high photoelectric conversion efficiency and expansion of the application range of the solar panels.