Algae, as a blue resource with high nutritional value and environmental regulation functions, have cell walls and extracellular matrices rich in various functional groups. These characteristics enable algae to easily accumulate harmful heavy metals such as lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) from the environment, posing potential food safety risks. This paper systematically reviews the sources, accumulation mechanisms, and speciation of heavy metals in algae, with a focus on the principles, effects, and applicability of major removal techniques including physical (heat treatment, ultrasound, high pressure, etc.), chemical (acid washing, chelating agents, natural deep eutectic solvents), biological (fermentation, enzymatic hydrolysis, microbial conversion), and adsorption methods. Additionally, the potential applications of combined multi-technique approaches are explored. Current research faces challenges such as insufficient understanding of speciation, the difficulty in balancing efficient removal and nutrient retention, and the underdevelopment of green processing routes and industrial support systems. Future research should focus on multi-scale mechanistic analysis, the development of green mild processes, and the strengthening of industrial application frameworks, aiming to enhance the food safety of algae products and promote the high-quality development of the industry.