The piecewise linear current density recursive convolution finite-difference time-domain method of plasma is used to study the defect mode properties of transverse magnetic wave propagation in the two-dimensional unmagnetized plasma photonic crystals with a line-defect layer. In frequency domain, the transmission coefficients of electromagnetic differential Gaussian pulses are computed, and the effect of lattice constant, dielectric column radius, periodic constant, parameters of plasma and parameters of line-defect layer on defect mode properties of two-dimensional unmagnetized plasma photonic crystals are analyzed. The results illustrate that the frequency of defect mode cannot be tuned by changing periodic constant, position of the defect layer and plasma collision frequency, but be tuned by changing relative permittivity and radius of dielectric column in the defect layer, and central distance between defect layer and dielectric layer with the width of prohibit band gaps fixed. Furthermore, the defect mode and the width of prohibit band gaps can also be tuned by changing lattice constant, dielectric column radius and plasma frequency.