In contrast to conventional band gap determination of Hg1-xCdxTe by low- temperature Fourier transform spectroscopy, we report the application of tunneling spectroscopy (STS) technique to measure the energy band gap of the vacancy-doped P-Hg1-xCdxTe grown by liquid-phase epitaxy (LPE) method. The apparent zero-current gaps measured by current-voltage tunneling spectroscopy are influenced by the imaging bias. However, the real energy band gap can be revealed by the normalized differential tunneling conductance, which were obtained using the lock-in amplifier technique. The results indicate the feasibility of room temperature band gap determination by the STS technique.