Sure. Put the total in an account, and have a check issued to her monthly.
Or, better yet, buy an annuity. Let's say that there are 100 months remaining before the CS ends and let's say that you need to pay $1000 per month. You could put $100,000 into a non-interest bearing account and everything would be OK.
Or, you could put less than $100,000 into an interest bearing account - but you have to guess how much the interest will be (or make an adjustment at the end). Generally, fixed interest accounts pay low interest, so you might put in $95,000 and be OK. Downside is that you'd pay taxes on the interest.
Or, you could buy an annuity to pay $1,000 per month for 100 months. Depending on interest and terms, you might only have to put in $80,000 to $85,000. Plus, if you set it up properly, you shouldn't have to pay taxes on the interest.
But I'm curious why OP wants to do this. Aside from the fact that your money will be tied up for a long period, it may be a waste of effort, anyway. Child support can be modified, so any plan you make today may not be relevant next year or the year after.
ETA: Of course, all of that assumes that child support is current and you're only talking about future payments. The way you phrased it ("Pay off child support") suggests that the amount might be in arrears. If that is the case, you must either pay it off all at once or reach an agreement with the court (or an agreement with your ex and then file it with the court) to allow monthly payments.