There were a number of different kinds of jobs that were done by the Chinese who came to the United States during the time you mention.  The link below has an excellent and detailed discussion of this topic.

Some of the main jobs done by the Chinese were the following:

• In Hawaii, the Chinese were brought over to work as laborers in the sugar plantations.  So these Chinese started as agricultural workers.
• On the mainland, many Chinese worked building the railroads that were booming during this time.  This was very difficult and dangerous work.
• After the railroad jobs petered out, many Chinese moved to cities and started working in things like restaurants and laundries.

Once again, please follow the link for more information.