Analysis on inoculated cast iron HT300 surface layer microstrutures of non-transformation hardening, laser transformation hardening (LTH), laser shallow melting (LSM) and melting are presented by selecting different laser energy densities during laser strengthening treatment. And the processing for slot bottom of shaft end with laser transformation hardening are also discussed. The results show that laser transformation hardening treatment is satisfied the processing requirement. The optimization of laser processing parameters: laser power( P ), laser processing speck diameter( D ), and laser scanning velocity( V ) are obtained by taking a lot of experiments. The comparative results of hardness and abrasive resistance measurement show that hardness and absolute weared volume of HT300 samples processed by LTH/LSM are increased by 7%, 34% and decreased by 13%, 25% respectively than those of surface induction quenching. Practically LTH is simpler than other processing methods and the experimental results provide a reliable basis for processing the slot bottom surface of shaft end.