Among the currently developed multi-principal element alloys (MPEAs), Ti-V-Ta MPEA stands out for its good high-temperature strength, good room-temperature plasticity, stable organizational structure, and low neutron activation, making it a prime candidate for cladding material in special power reactors. The radiation resistance of Ti-V-Ta MPEA is the focus of current research. Dislocation loops are the main irradiation defects in Ti-V-Ta MPEA, which can significantly affect the mechanical properties. Therefore, clarifying the formation mechanism of dislocation loops in Ti-V-Ta HEA can help understand its radiation resistance. The formation behavior of dislocation loops in Ti-V-Ta MPEA was studied based on molecular dynamics method. Cascade overlap simulations with vacancy clusters and interstitial clusters were carried out. The cascade overlap formation mechanism of dislocation loops was analyzed and discussed. In Ti-V-Ta MPEA, the cascade overlap with defect clusters can directly produce different types of dislocation structures. The defect configuration after cascade overlap is determined by the PKA energy and the type and size of the preset defect clusters. Cascade overlap can improve the formation probability of <100> dislocation loops in Ti-V-Ta MPEA. Cascade overlap with vacancy clusters is an important mechanism for the formation of <100> vacancy dislocation loops, and the size of vacancy clusters is the dominant factor for the formation of <100> vacancy dislocation loops. When the PKA energy is enough to dissolve the defect clusters, <100> vacancy dislocation loops are more likely to form. Furthermore, cascade overlap with interstitial clusters in Ti-V-Ta MPEA is a possible mechanism for the formation of <100> interstitial dislocation loops. This study can help to understand the evolution behavior of irradiation defects in Ti-V-Ta MPEA, and provide theoretical support for the composition design and optimization of high-entropy alloys.