I am 3 weeks pregnant and I am working as a laser hair removal technician. Is it harmful for me and my baby?

Hi Cheng.  Although there is no research to support whether it is safe or harmful, but we do know that lasers are "non-mutagenic".  This means they are not cancer causing devices like x-ray machines.  Because lasers are light, they are completely different than the type of exposure that you get with radiology (x-ray) and there should not be a risk of working while performing treatments.

Thank you for your question. Even though there is no research to show whether lasers used for laser hair removal are safe or harmful, we do know that the lasers do not cause cancer. Therefore, there should be no risk of working while performing treatments. I hope this helps!

Good question to ask, but difficult to answer. Difficult to answer because the type of equipment is unknown and I know of no studies that provide reasonable guidance.
Pregnancy is such a sensitive topic, I would not hazard an opinion with the information provided. I suggest you contact the manufactures representative of your laser equipment for possible guidance.     
If you're not satisfied with their response, you may wish to step back for a while. It's not just the light you should be concerned about. Some lasers have a surprisingly strong electromagnetic pulse with each flash.
Wishing you a wonderful baby and long enjoyable life together. 
Warmly,
Arbella Sarkis, MD