I was on STEM OPT VISA till Oct. From Oct1 my status had been changed to H1B.I got married on 19 Nov18.my spouse is here on H4.Am I eligible for resident join filing tax?

[KarenJ]

When did your spouse arrive in the US.  How long has your spouse had the H4 visa?

[LinaJ2018]

It depends. 

If you have already stayed in the US for more than five years and 2018 is at least your 6th year in the US, you are considered as US resident for tax purposes.  You can file a statement to treat your nonresident spouse as a resident. See   Nonresident to resident .  You can file Married Filing Jointly.