The experimental set-up of a red picosecond pulse output from a ultrashof t cavity dye laser pumped by third harmonic from a colliding pulse mode-locked Nd:YAG laser is reported and the experimental results is presented in this paper. The dependences of the output laser wavelengths of chl a and b in different aggregations in solutions on the dye concentrations are studied. As chl a-ethanol solution with concentration of 2 × 10-3M and the length of the laser cavity less than 36 μm, a single mode-tun blea ps pulse train coula b=obtainea. Divergence angle of the laser beam ia about 60 mrad.