We design a multifunctional molecular spintronic device consisting of two 1,3,5-triphenylverdazyl (TPV) radicals with carbon nanotube bridge and electrodes , and investigate its spin-polarized transport properties using the first-principles density functional theory and nonequilibrium Green's function method. The results show that the spin-polarized transport properties depend strongly on the external magnetic field modulation and high-efficiency spin-filtering, giant magnetoresistance , spin-rectifying and low-bias voltage negative differential resistance effects can be realized in this designed device. The mechanisms are proposed for these interesting physical effects based on the bias-dependent spin-resolved transmission function, projected density of states and corresponding molecular projected self-consistent Hamiltonian orbitals analysis. These results hold great potential for the development of high-performance multifunctional molecular spintronic devices. High-efficiency spin-filtering, giant magnetoresistance, spin-rectifying and low-bias voltage negative differential resistance effects are realized in a TPV radical-based molecular spintronic device with carbon nanotube bridge and electrode. • Spin-polarized transport properties of a TPV radical-based molecular spintronic device are investigated. • Spin-polarized transport properties depend strongly on the external magnetic field modulation. • High-efficiency spin-filtering, GMR, spin-rectifying and low-bias voltage NDR effects are realized.