This study investigated the spatial distribution and risk levels of cadmium (Cd) and lead (Pb) contamination in farmland soils within a typical industrial and mining area of northern Guangdong. An evaluation framework centered on “total content-chemical speciation-bioavailability” was constructed to provide a scientific basis for regional soil heavy metal pollution control and remediation. Taking the specific farmland area around typical industrial and mining industries in northern Guangdong as the research object, field sampling and laboratory analyses were conducted to determine the total concentrations and chemical speciation of Cd and Pb. The contamination degree, ecological risk, and bioavailability were systematically assessed. The results showed that: (1) both the contents and evaluation indices of Cd and Pb exhibit strong spatial variability. The spatial distributions of high-concentration areas differ between the two elements, indicating distinct pollution sources. Cd, in particular, displays significant point-source pollution characteristics. (2) Cd showed a high level according to the potential ecological risk index, whereas Pb was classified as uncontaminated based on both the single-factor index and the potential ecological risk index. However, the risk assessment code (RAC) and reduced partition index (RSP) evaluations for Cd both indicated high contamination levels. For Pb, RAC results suggested mainly low to moderate risk, while its RSP result indicated high contamination. The pollution grades derived from bioavailability-based assessment (using chemical speciation) were higher than those based on total heavy metal content. The soils in the study area were predominantly acidic, which could enhance Cd bioavailability and lead to a high contamination risk. Although Pb was considered safe based on total content evaluation, its potential ecological threat remained significant. Priority should be given to the remediation of Cd, while long-term monitoring of Pb should be strengthened to mitigate the composite pollution risk in the farmland ecosystem.