Plasma temperature and electron number density are important factors of the laser-induced breakdown spectroscopy (LIBS) measurements. The plasmas are generated using two 532 nm NdYAG pulsed lasers to ablate the plasma breakdown liquid jet of CaCl2 solution. We get the spectrum of 300~450 nm band and analyze the Ca II emission lines. It is assumed that the plasmas produced in the experiment are in local thermodynamic equilibrium(LTE), according to LIBS formula the Ca plasma temperature of 104 K is determined by using the Boltzmann plot method with 6 Ca II lines while the electron density of 1017 cm-3 is obtained from the Stark broadening of Ca II 393.366 nm line. The variations of plasma temperature and electron density with delay time and the time between two pulses are discussed based on experimental results. The advantage of double-pulse LIBS over single-pulse LIBS is proved. Experimental results show that the laser induced Ca plasma is in local thermodynamic equilibrium.