The invention discloses a composite passivation material suitable for the arsenic-cadmium-lead polluted rice field, and an application thereof. A preparation method of the composite passivation material comprises the following steps: (1) preparing rice straws; (2) preparing a hydroxyapatite suspension; (3) preparing a composite passivation material; and (4) carrying out pyrolysis sieving. Crop straws used as a raw material are mixed with the hydroxyapatite suspension and an iron salt solution according to a certain solid-to-liquid ratio and a certain reaction sequence, and determination of thereaction sequence and adjustment of the pH value of the solution in the process are combined with microwave, ultrasonic sound, mechanical stirring, high-temperature oxygen-limited pyrolysis and othertechnical means to form the composite passivation material containing biochar, hydroxyapatite microspheres and nano-iron. The prepared composite passivation material has the advantages of obvious reduction of the bioavailability of arsenic, cadmium and lead in soil, reduction of accumulation and conversion of arsenic, cadmium and lead in rice grains, stable and durable passivation effect, and small negative influences on crops and the environment when applied to the arsenic-cadmium-lead polluted rice field.