The mobility, bioavailability and toxicity of arsenate (As) in soils are restricted by its species. Humic acids (HAs) are important factors affecting the fractionation of As in soils. An indoor cultivation experiment was conducted to discuss the effects of the two active components of HAs (fulvic acid, FA; and humic acid, HA) and HA/FA ratio on the transformation of As in soils. The results showed that FA and HA had significant effects on different As species in soils, and the influence degree and direction were connected with HAs concentration, proportion of FA and HA and exogenous arsenic content. FA and HA with carbon content ≤1% increased the content of exchangeable As, but HA with carbon content ≥3% decreased the content of exchangeable As (Ex-As). FA and HA decreased the content of As combined with aluminum (Al-As) and iron (Fe-As), and increased residual As (Res-As), and FA was stronger than HA in effect. Under the condition of the same amount of HAs, when HA/FA ≥5/5, HAs decreased the content of Ex-As, but when HA/FA≤3/7, HAs increased the content of Ex-As. With the increase of exogenous As content, Al-As increased, Ex-As and Res-As decreased, Fe-As first increased then decreased. Ex-As and Ca-As had the largest contribution to effective As in soil. HA reduced the effectiveness of exogenous As in soil, but FA in low concentration (≤3% C) increased the bioavailability of As to a certain extent. It is important to control the reasonable amount and active component ratio of organic material when using it as As regulator in soil.