A single-mode InGaAsP/InP buried heterostructure (BH) laser based on high-order slotted surface gratings has been fabricated. The introduction of surface slotted grating can simplify the fabrication process of single-mode BH lasers notably. The laser shows a good single-mode emission performance, with larger than 30 dB side-mode suppression ratio (SMSR) when the current is between 200 and 400 mA. Calculations show that the gain coupling mechanism plays a key role for the slot grating to select the emission wavelength. The linewidth of the laser is measured. The fitted Gaussian and Lorentzian linewidths are 1500 and 550 kHz, respectively.