Objective To investigate the effects of gastrocnemius muscle forces on biomechanical mechanism of heel pain. Methods The finite element model of the foot including foot bone, soft tissues, ligaments and plantar fascia was reconstructed based foot CT images by Mimics software. The gastrocnemius force applied on the foot was 40%-90% of half-body weight（320 N） with increment of 5% of half-body weight（16 N）. The plantar surface pressure distribution and peak pressure as well as the plantar fascia stress were calculated. Results The plantar surface pressure distribution was mainly concentrated on the heel and metatarsal head. With the increase of gastrocnemius force, the peak plantar pressure at the heel decreased, while the peak pressure at the front of the foot decreased at first and then increased, which reached the minimum value with the load of 224 N. The plantar fascia stress increased with the gastrocnemius force increasing. Conclusions Gastrocnemius force applied on the foot has a significant influence on the plantar pressure distribution. Finite element analysis can contribute to understanding etiology and pathology of foot diseases, predicting the biomechanical results of the treatment and provide theoretical reference for treatments.